New Year

Have a Happy and Safe New Year. Looking forward to working with (nearly) all of you in 2010.

Have a Happy and Safe New Year. Looking forward to working with (nearly) all of you in 2010.

.... and keep thinking physics, its what's all around you.

Honors Assignment on Magnetic Fields and Forces

Read the notes posted here. Answer the sample questions up to but not including the ones on Magnetic Induction - except the generator groups, you get to do it all.

I'll try to write some notes on plasma particle and energy loss in the next day or two, so make sure you stay tuned.

http://h1.ripway.com/DrCherdack/Notes%20on%20magneticsR8.doc

Honors Fusion Power Plant

I will try to post notes and problems on plasma, heat transfer, thermodynamics, magnetics, and structures on a general level so you all can have an overall grasp of the physics behind the entire plant. As you may imagine, this may take some time so keep checking this space. At this point I believe, each group should have some understanding of their own specialty from reading notes and the relevant passages in your text. You should be meeting.

By the way, the I in magnets is current, i.e. amps or Coulombs per second; and NOT impulse (which of course is J for Jimpulse).

Archimedes Lab

Many of you folks still miss the point. We did not need to use a lab to find a number we can get out of a table, e.g. the density of the brass block. The purposes of our labs are almost always to confirm an hypothesis we formed from observation and translated into equations or one we derived from other related observations and proved hypothesis.

The main purpose of this lab was to demonstrate that FB = rho g Vol sub. If, by using a volume obtained using this equation, we got the right density, then the equation is correct. Errors of a few percent in the measured vs expected value of density offer pretty compelling confirmation of our equation, i.e. Archimedes principle

The second purpose was to try to verify that change in height of a fluid changes the pressure in a vessel according to delta P = rho g delta h. Many of you were much more succesful in this than I expected, getting errors of 10 % and lower. Good work.

AP Break Package

Here is a link for the first part of the package. Make sure you read the handwritten notes for the oscillation questions ('95 questions 1 c and d). Also skip the '94 question you are not ready for it. [it just kind of snuck in there].

http://h1.ripway.com/DrCherdack/APDecBrkPckg.PDF

Greetings

Hope this Christmas has been a a happy one for you. While this time has a particular meaning for those who celebrate Christmas, this break in our usual pattern of life is a good time for all of us to think about those people who, and those things that, make life worthwhile... and I don't mean Brad Pitt or new ipods.

Make the best of this time and I'll save my tirades about your lab reports for some other time.

AP Assignment

Complete the review package by tomorrow morning,. It will be counted as 6 homeworks.


All right; stop your whining; its due Monday right after break.

For those who were out, here's a link to part of it. I may get the rest up soon or even during the break so keep checking.

http://h1.ripway.com/DrCherdack/AddlMechRevQuest08-9.doc

Honors Assignment

Read the notes and do the problems in the notes and WS1 tonight.

http://h1.ripway.com/DrCherdack/Reaction%20Rates.doc

http://h1.ripway.com/DrCherdack/Nuclear%20Reaction%20Rates%20WS%201.doc


http://h1.ripway.com/DrCherdack/Nuclear%20Reaction%20Rates%20WS%202.doc

AP Package

There is a two part Mechanics Review package in your out file. Make sure you get both pieces. You'll be doing it over break and its worth 6 homeworks

Honors Homework

Assume:
electric power needed is 750 MW,
efficiency of conversion of fusion power to electricity is 45 %
plasma volume is 200 cubic meters
energy per reaction is 2.9 E-12 J
assume nD = nT = 1/2 of N fuel [ number of fuel nuclei per cubic meter]
sigma v is 7 E-22 cubic meter per sec [yes these are the units for the reasulkts to come out correctly]

Find the following:
fusion power required
fusion power per cubic meter of plasma
reactions/ ( cubic meter sec) required
nD , nT

20 extra credit points if you get it right, show all work and DON"T just copy

Fluid Review Solutions

Hopes this helps

http://h1.ripway.com/DrCherdack/Soln%20Sh%20Fluid%20Dynamicsr1.doc

Honors

We will be spending the next three days on projects. You will also have a large assignment on your project over the break.

Your assignment for Monday is:

All re-read the relevant sections of the European power plant report. This means the summary and whatever annexes apply to your specialty.

Plasma and blanket groups have some real meat to digest right in the report. Plasma group, identify density (number of fuel nuclei per m cubed), volume of plasma and confinement time. Start to understand energy and particle loss mechanisms.

Heating group should go back to the ITER website and be clear on power, energy, currents, type of ions, etc. You should also be clear on microwave heating including the ion and electron cyclotron frequencies and powers produced for ITER.

Magnet group. Make sure you understand the directions and purposes of the OH, Toroidal , and Poloidal fields and the configuration of the coils that produce them.

Read these notes [don't panic we will go over them in class]:

http://h1.ripway.com/DrCherdack/Notes%20on%20magneticsR6.doc

http://h1.ripway.com/DrCherdack/TokamakFields.doc

Plasma group read the above notes also.

Thermo group. Read this

http://h1.ripway.com/DrCherdack/Notes%20on%20Steam%20Cycles.doc

and then look in text to understand thermal conduction. Heat must be transferred from lithium to water/steam by passing through tubes containing the water/steam that are immersed in the lithium. Find the equation for this heat transport and figure out the following: assume the tube wall is 1 cm thick. Assume the temperature difference between the water/ steam and the lithium is about 200 C. How many square meters of surface area are required to transport 2.5 E9 Watts of thermal power. Look up Rankine cycle and steam turbines. Identify 4 web pages that will help you design your turbine cycle.

Generator group: read text on magnetic fields and magnetic induction. Know Faraday's Law and what it means. If the changing field goes from +B to-B in 1/120 th of a second, and the coils that the voltage is being induced in have 100 turns and a coil area of 2 m square, what is the required value of magnetic field strength B to produce 20,000 V in the coil. The coil will be wrapped around soft iron so mu is not mu 0, its about 1000 mu 0 ( mu is the greek letter that looks like a fancy u).

E mail

You guessed it: can't reach our school email again.

AP Fluids Problem Sheet

This is a newer version of the fluids problems which addresses some refinement of the wording of some problems, etc.

http://h1.ripway.com/DrCherdack/Unit%207%20AP%20Prob%20Sh-06R2.doc

Ballistic Pendulum Lab

Too many labs say delta PE = delta KE. This is not true. Everyone should be aware that IF Win adn Qin adn delta Eth all =0, then delta PE equals the OPPOSITE of delta KE, i.e PE gains what KE loses and vis versa.

In this particular lab all the KE right after the collision becomes PE when the motion stops. Thus for the period beginning when the collision ends, and ending when the pedulum reaches maximum height, delta KE = O- KE' = -KE' so delta PE = --KE' or KE' = delta PE, but only in situations like this and note again that KE' is the intial KE befoer the PE starts to increase.

All Juniors Physics SAT II

Many of you should considering taking the Physics SAT II test. Only about 50,000 take it and so even just doing okay on it may help you get into some place you probably don't belong........ I mean you will appropriately challenged. I will do after or before class coaching from about mid May to the first week of June. If you are in AP, taking the SAT II in May might work, but June would be better. June would definitely much better for honors.

Honors test

Because the PSAT scores will be given out in science classes tomorrow the Honors Test may be divided into two parts with the nuclear and 2 D problem given on Friday. We'll see how it goes.

Email

Surprise Surprise, our email's not working. I can see you've sent messages, but they won't open in Internet disaster or firefox, so I an' read what you're asking me. Sorry

Collision and fusion problems

Here are solved copies of recent classwork problems. If this link doesn't work its also posted on the homework page on my oncourse website

http://h1.ripway.com/DrCherdack/samplecoll%20probs.doc

Missing Medical Program form

Someone removed the form for the Youth forum on Medicine from my computer desk. Please return it ASAP.

Bring Cans by Noon

Last chance to show you care about others, do it!

Honors Assignment

Complete problem 1 on Collision Worksheet1 and problem 1 on Collision Worksheet 2 and do problem 9 on the "Extra Problem Sheet ..... and I have no idea why anyone is using a 1.2 kg bowling ball.

Collision Worksheet 2 Problem 1

Ignore, in fact cross out, the words in parentheses. Just find delta p in the x direction and in the y direction. The momentum transferred to the blade would be would be the same magnitudes but in the opposite directions ( x instead of - x and -y instead of y). Energy transferred to the turbine blade is just KE lost by the steam.

Honors 2D Momentum and Forces

Lets do some two dimensional collisions. Problem one on Collision WS1 and problem one on Collision WS 2. These were posted on 11/15. What you have to remember is that the momentum equations now work as 2D vector equations.
m1v1x + m2v2x = m1v'1x + m2v'2x and m1v1y + m2v2y = m1v'1y + m2v'2y and of course components, components, components.

Future Doctors

There is a program called the National Youth Leadership Forum on Medicine. While I believe it is costly, I have heard good things about it from students in the past. If you would like to consider it you must tell me by end of school Wednesday. If you do consider it, I would suggest you check it out carefully before you commit, but that is well after I nominate you, so tell me ASAP if you want to be nominated.

Calculators

I have one with a girl's name beginning with C carved into it. The office has about eight.

Honors 2 Labs

i need to discuss labs with Scott, Harold, JB, Dean, CJ, Maria, Ben, Jen, Monica, and, not to be left out, Tony. See me before or after class but no missing gym.

AP 2 Labs

Missing grades on labs from Brad, Cal, Wave, John, Katelyn, and Armon. See me before or after class- no being late to next class though.

Honors 1 Labs

Missing grades on labs from Miguel, Claire, Stephanie, and Carly. See me before or after class- no being late to next class though.

( I'm not missing any labs from Ashley and those brownies were too good.)

AP 1 Labs

Missing grades on labs from Jay, Audrey, David F and Scott. See me before or after class- not being late to next class though

AP Test Results

I am mulling over how to treat your test scores. The test was straightforward and not all that difficult or long, but I did not provide any equations, etc. and you do deserve some credit for getting most of that stuff right.

I'll let you know in a day or two and then post it on Home Accident.

Honors Test 2 items

1) There will be a sort of retest on Thursday, it will include a question or two on 2 d forces or momentum, but mostly a retest of the most recent disaster.

2) Your grade on the last test is the greater of your score x 1.25 or your score + 17

AP Power and Energy 2 items

1) Some folks are still missing the point: power is the rate of transfer or transformation of energy. It does not have to go into changing Ek. When a car is accelerating up hill, power from the engine is going into raising EP, EK, and combating friction and air resistance ( changing Eth and overcoming losses to outside the car - call these losses to outside a negative Qin) all at the same time. These are all the things that can comprise work and power is just the rate at which work is done.

Mav is only the rate of change in Ek. Mav usually = Fnet v, but power from a force involves the total of that force, not just what is left over after subtracting the forces opposed to it. If you don't believe me run up 100 flights of stairs at a constant speed (Mav =0) and let me know how little power it and work it took. The power supplied by a particular force may usually be found from multiplying that force by the velocity in the direction of that force, but this not fool proof. Consider two train engines or bulldozers (or Sumo wrestlers for that matter) of different powers pushing in opposing directions. The engine that is overpowered is exerting a force opposite the velocity but it is not putting out negative power. Its power is going into friction or tearing up the earth or ripping apart metal. The work kinetic energy theorem is incomplete at best and downright misleading often.

2) AP Section 2 tests - I am the nameless committer of the error. Thus the need for reclaiming your tests. Put them in the test folder Monday.

Honors

You should be able to do AP Worksheet 3 problem 2. Remember that velocity of plane as seen from ground is velocity of plane as seen the by air plus velocity of air to ground ( i.e. wind velocity). All addition is by components. Keep in mind that the velocity of the plane with respect to the ground has a zero component in the North direction. Use this to find the north component of the plane's airspeed and then use that to find the angle of the plane's air speed.

AP Section 2

Someone who shall remain nameless made an error in his answer set. Please return your tests on Monday.

AP Two Items

1) Please change the header in the unit 7 schedule to 09-10. It really is a new schedule but I do use the old version for formatting.

2) Section 1 . There was no typo. I had changed the question ( made it simpler) to match the answer rather than correct the typo in the answer. I just forgot I had done that.

AP Fluids Schedule ( Unit 7)

Here it is, the unit that is all wet (well not really gases are fluids too.) In ADDITION to schedule Read Notes on Archimedes by Tuesday 12/15. Also do Fluids Dynamics WS by
Monday 12/21
http://h1.ripway.com/DrCherdack/APUnit7Fluidsched-09-10.doc

http://h1.ripway.com/DrCherdack/NotesonFluidDynamics.doc

http://h1.ripway.com/DrCherdack/NotesonArchimedes.doc

http://h1.ripway.com/DrCherdack/Archimedes%20Lab%2012-08.doc

http://h1.ripway.com/DrCherdack/Unit7APProbSh-05R1.doc

http://h1.ripway.com/DrCherdack/ReviewShFluidDynamics.doc

http://h1.ripway.com/DrCherdack/Fluid%20Dynamics%20Worksheet%20.doc

AP Assignment for Unit 7 Fluids

Start our study of fluids off with the following readings : Text Section 13.1 then pages 378-80, then section 13.2 and then up through page 422. Answer conceptual questions 1,2,3,5,6 ( don't you hate those "know-it-alls" like Susan?). Also read Notes on Fluid Dynamics Sections 1 and 2.

http://h1.ripway.com/DrCherdack/NotesonFluidDynamics.doc

Honors Assignment 2D Motion Continued

Complete AP Unit 2 Worksheets 1 and 2 and do problems 1 and 2 on Worksheet 3.

Use the table of components method we used in class and identify your angles carefully.

Magnitude is found by applying Pythagorean Theorem to the components ;
magnitude of C = sqrt( Cx^2 +Cy^2).

Direction is found from: angle from horizontal axis is angle = tan^-1 ( Cy/Cx).

Remember the velocity of A as seen from C is velocity of A with respect to B plus the velocity of B with respect to C. All addition is by components.


http://h1.ripway.com/DrCherdack/Unit_2_Worksheet_2_.doc

http://h1.ripway.com/DrCherdack/Unit_2_Worksheet_3.doc

Honors Section 1

I think we forgot to change the ship's velocity to 10 m/s in the components table. So lets just say the ship sped up and was now going 22 m/s when I threw the ball. Then our table will be correct. Change the sketch in your notes accordingly.

If you finished both AP sheets and the crate problem, all you have to do tonight is problems 2 and 3 on AP Unit 2 WS 3. See the next post to download it.

Weekend Assignment

I have been reading through your assignments. Thank you for sharing your thoughts. I will hold on to these reread them more than once I'm sure.

Honors Assignment

Do this problem and complete the AP worksheets if you can and think components.


http://h1.ripway.com/DrCherdack/2%20D%20Force%20Worksheet%201r1.doc

CANS!!!

Lets not prove folks they are right about you guys being self absorbed , inconsiderate, and all those others things we know ( sort of ) are not true. CANS !!!!

Governor's School Etc

Some of you should be thinking about outside opportunities like governor's school, Rutger's astrophysics program, science programs at Columbia, summers or weekends at Princetion Plasma Labs, etc. See me for more info

Vectors and Magnitude

Magnitude is just how "big" something is. The magnitude of a velocity is the speed; the magnitude of a displacement is its length; the strength of a force is its magnitude. It has same units and almost same meaning as the vector itself, just without the direction.

Honors Assignment.

Here is a an assignment aimed at helping you think about some mathematical operations. The second sheet is the real assignment but play with the first sheet for a while.Try moving the green and red blocks to help you see what each contains; ask yourself some other questions relating to multiplication and division. Also, look over the review sheet. If you have energy or time left try to finish the AP Unit 2 WS also.



http://h1.ripway.com/DrCherdack/Mathematical%20Operations.doc

http://h1.ripway.com/DrCherdack/Hnr%20Math%20Rev%2010-08.doc

http://h1.ripway.com/DrCherdack/Math%20Rev%20%20Hon%20Phys06-07.doc

AP Homework

Tomorrow, please tell me how long it took you to do the homework assignment for this past weekend and how much of it you were able to complete.

AP Power Sheet

When it asks for power for the cars find average power.

Finding power at beginning and end of an acceleration would also be interesting and you can do it if you assume all work is doing is changing KE and acceleration is uniform. [but you don't have to do these]

Honors Assignment

Reread Sect 3.1 -3.5 Answer question 7 ( think about your lab) and problems 9 and 10.

Also try this worksheet

http://h1.ripway.com/DrCherdack/Unit_2_worksheet_1.doc

AP Section 1

1) If you had a test where the MC answers were DBCAD or were about DBCAD (not AABBA) turn it back in. There are more points coming your way.

2) More cans NOW!!!

AP Rotational Energy WS

Hot off the press. In problem one, the radius of the wheel is 30 cm.

http://h1.ripway.com/DrCherdack/Rotational%20Energy%20Worksheet.doc

AP Homework Assignment

Here is the link to the Power sheet.

The rotational stuff will be up soon.

http://h1.ripway.com/DrCherdack/PowerandEfficiencyWorksheet.doc

Food Drive

There are no food cans in 506 right now. Change that ASAP

Tuesday 12 /8 periods 5, 6, and 7

As you know, Mrs. Fern Wilson died last week. She was one the finest people and teachers I ever knew. I will try to attend her funeral periods 5,6,and 7 on Tuesday as a mark of the respect and affection I hold for her. If you knew her or know someone who did know her, please reserve a minute of thought for the passing of a wonderful person.

No email

Our email has been down since about 4PM Friday. What else is new?

Assignments for all including Topics

Honors Chapter 3 read sections 4,5 and 6 do problems 7,8,10

Honors and AP special assignment on grades

Topics show c^2 t-r^2 = c^2 t'^2 - r'^2

Honors Assignment 2D Motion

We now start the dreaded subject......... VECTORS!!! ( can't you just hear that evil, blood curdling laughter in the background) Read Chapter 3 Sections 1,2,3 Do problems 1,3,5.

Canned Food Drive

Donations have tailed off dramatically. Please think of others who are needy. You can do it

AP quiz and Lab Due Date

There will be a 1/2 period quiz tomorrow covering KE, PE, work, and losses. Not power or rotational energy. Section 1 ballistic pendulum lab is now due Friday - there is only so much whining I can stand.

AP and Honors Labs

A few of you continue to not turn in labs on time. Starting this week labs one week late lose a letter, labs more than 5 school days overdue will receive a zero. Returned labs to be resubmitted will be due no later than 6 school days after returned. No labs due before Thanksgiving will be accepted after this Thursday.

AP Momentum Lab

I would like to tie in the momentum lab with enrgy conservation during collisions. I had asked you find out how much KE was lost during the collisions. This takes writing about five equations and copying them for each run. I would like you to identify which runs had the greatest losses and see if you can explain why. Do this with a paragraph or two citing percent differences and characteristics e.g. both carts moving , lots of bars, or whatever is appropriate. Bring it in tomorrow.

Thanksgiving

One good way to give thanks is to help others, so put those cans next to your book bag now. This way you won't forget them on Monday. Oops, shouldn't mention Monday on a holiday weekend.

AP Ballistic Pendulum Lab

We did not complete the lab with the ballistic pendulum yet. We just found vsphere, but we haven't checked it yet. We will complete it Monday or tuesday and the lab will be due the second day after that.

AP and Honors

Just a reminder, work = F x displacement in direction of force. For most cases we deal with work = area under force vs displacement graph. More accurately, work is the area between the force curve and the F=0 axis because work is negative when force is in opposite direction of displacement which would show up as a curve under the F= 0 axis.

AP Retest

A retest will be available for all those who got a raw score of below 85 on the momentum test. It must be taken on Monday and you must let me know by email before Monday if you want to take it.

Thanksgiving

During this Thanksgiving break take a good look around you. I hope you see lots to be thankful for.

Take some time out to say thank you for all the good things. Say it quietly, inside where you feel it, and say out loud to those who should hear it from you.

While I am reminding people to be thankful, I will say thank you to you folks for trying to learn.

Grade Changes

I have put in some grade changes you might want to look at. In honor of the holiday I refrained from all those major reductions in grades I had planned on and I did raise a few.

Rockets Again!

Here is the link to the better but not great rocket data and calcs. I understand off course is off the rails once again.

http://h1.ripway.com/DrCherdack/Katelyn%20SrcktcalcR1.xls

Honors, AP and Topics

Now is the chance to show people that you are not all self centered, grade grubbing, egotistical, megalomaniacs. Now you can show people that you are caring, kindhearted, and supremely charitable to the less fortunate around you. In other words now is the time fool everybody. BRING IN THOSE CANS.

Calculators

Please check to make sure you are carrying around your own calculator as 506 students are missing a few. I know someone has David Shang's for instance. Please return them to the prpoer owner or me ASAP.

Opportunity in April

I received this from Ms. Van Der Stad, a 4th grade teacher at Oak Street. Please let me know ASAP if you are interested. We would start planning in march. Could be fun to build our own and see if we can beat 4th graders, oops, I mean assist 4 th graders. Also could be a nice way to wind down from the Jnauary physics olympics.

Thanks so much for being excited about an opportunity at Oak Street! We have four 4th grade classrooms. Basically, we are looking for two groups of 4 students (8) to come down to Oak Street (for a 2 hr. block) and do some sort of experiment and/or discuss the concepts of Motion and Design. Each group of 4 students would present the same information in two classrooms.

We will be starting this unit probably in April. So, any time during that month would be wonderful.
In the 4th grade Motion and Design Unit, students work with Kinnex to create cars. With the cars they do different tests to see how the change of shape or addition of other materials (sail, fan, thicker rubber band) change the speed of the car.
If any h.s. students would be willing to come down, our students would love it!

Any ideas of what the h.s. students could talk about/ show them would be great.

AP Section 1 Momentum lab Spreadsheet

I checked the file I tried to upload.It has values not equations. Apparently when our network uploaded the file it went to an earlier version saved somewhere on our servers. This also happens once in a while when I print something.

Revised Rocket Lab

Sorry guys but there was an error in the last spread sheet for the rocket lab. Here is a revised copy. The data is faulty and our assumption about a being constant during the burn is also faulty. The rocket acclerates more at first so it actually reaches close to vf soon after launch.This means that vf is closer to vavg. However, that's one thing a lab does. It let's us know where our assumptions are out line. Using ttop - tbo gives a height based on vbo. The column other gives a height based on vbo squared. Thus the discrepancy between the two Htop- hbo columns shows our vbos are probably too high.This explains our impulses and heights being higher than expected.

My best guess about the data is that for the first run someone forgot that hbo was measured from 2 m from the pole so hbo is the cm sighted on the meter stick x 30 (/ 100 to get m) not x60 . Lets say that the first hbo is thus 1/2 as great. Lets see what happens when we divide this hbo by 2. see row 17 on the spreadsheet. We get poor, but not incredibly bad, agreement. Other possibility is that hbo was confused with htop. In any case here its ( well soon, still can't upload from here). I will post it as tonight's homework on Off course.

Publish Post

Honors Ballistic Pendulum Lab

This lab is formal because it needs a procedure otherwise who will know what you did? Discussion should include the calculations you made to find v' ( right after the collision of the sphere with the catcher) from the PE final which equaled the KE right after the collision and then how you used conservation of momentum during a collision and the ratio of m' the (total catcher + sphere mass) to the sphere mass to find v sphere before it hit the catcher. Note that the effective mass of the catcher was 116 g so m' = 116 g + mass of sphere. There should be references to conservation of energy ( how you found KE from PE) and conservation of momentum ( how you found v from v'). Note you cannot say you proved anything since we have not measured v sphere to see if your calculated value for v sphere was correct. You can conclude something about how you can use conservation laws to find things out.

Section 2 lab is due Tuesday but I'll give an extra day since the rocket lab was so tough. Section 1 is still due Wednesday.

Rocket lab

As of this time, the only nearly complete set of data I received was from Katelyn Stover and her group, Kevin and Armon. I took their data and enhanced it a bit and calculated Js and free flight heights. The equations I used are in the cells. Take all this and create a report showing that you understand the calculations and repeating them in your reports. Add a sample problem where you specify mass and rocket engine J and burn time and calculate v bo Hbo and H free flight ( Htop - Hbo). Lab will be accepted until Wednesday end of school.

http://h1.ripway.com/DrCherdack/Katelyn%20Srcktcalcs.xls

AP Energy and Work Unit Schedule

Here are the goodies. Also try reading the notes on energy fundamentals tonight and reread the notes on torque when we get to rotational energy.

http://h1.ripway.com/DrCherdack/AP%20unit%206%20Energysched-09-10.doc

http://h1.ripway.com/DrCherdack/Notes%20%20Work%20and%20Energy%20R5.doc

http://h1.ripway.com/DrCherdack/NotesEnergyFundament9-09.doc

http://h1.ripway.com/DrCherdack/Unit6%2009-10Work%20ws1.doc

http://h1.ripway.com/DrCherdack/Unit6%2009-10WS2.doc

http://h1.ripway.com/DrCherdack/unit6-09-10EnergyProbSht.doc

David Shang

Are you in possesion of someone else's calculator? If so please email me.

Momentum Spreadsheets

each group for all classes should have sent me a spreadsheet with formulas in the v, p, etc cells. Only the mass and time cells should have simply numbers. I am still missing a few ( about 5 of 24)

Honors Project Reports

By Monday each group should turn in one project proggress report on what you have accomplished since 11/11.

Study Group reports

Unit 5 study group reports should be in for all AP and it would be a good idea for honors as well.

Honors Assignment

Las night's assignment should have been Chapt 7 not 5 . Sorry. Do the Chapt 7 work for Monday. Focus on getting good rocket data tonight.

Topics in Physics

An oldie but a goodie so please review this if you were in my AP or read the first 8 pages tomorrow
http://h1.ripway.com/DrCherdack/NotesonSpecialrel15A.doc

AP Sect 1 Momentum Lab

I found the error leading to the 800% error. The time was missing a zero after the decimal point. There are still at least two suspect pieces of data and these are noted on the spread sheet with red colored cells and comments below. One I am pretty sure of the other, I don't really know.

I tried to load the file onto to my usual server, but I can't do it from school sites detect viruses when I try to connect???) so I'll load it at home and send you the link then. in the mean time I'll try to put it on offcourse ( my school website) as yesterday's homework

Calculators

I would like to thank the two generous students who have contributed their calculators to the room 506 inventory. In the unlikely event that you choose to renege on these gifts, please see me. and [ I am adding this at the request of a student] I love BROWNIES!!

AP Test

You are not responsible for angular momentum. In fact as far as I know, the only thing you are really responsible for is making a mess in my room and keeping here to all hours. However responsible or not, angular momentum won't be on the test.

You are also not expected to know anything about KE, or much else for that matter, but at least KE won't be on the test.

AP Chapt 9 prob 61

Use kinematic equation Dy = (vyf^2-vyi^2)/2a to find vyi immediately after explosion. Note that of this vyi 20 m/s was due to pre explosion velocity so delta v due to explosion = vyi-20m/s = 80m/s.

impulse upward from explosion on lighter fragement = impulse downward on heavier fragment

Since other fragment was twice as massive its Dv due to the explosion is 1/2 as great so it's v right after explosion = 20 m/s( the pre-explosion v) -80/2 = -20 m/s

Honors homework help

for problem 1 note v1 ' = - 1.8 m/s and then use conservation of momentum to find v2' = 6.77 m/s. Then find KE -KE' suing v1 for initial KE and v1' and v2' to find KE'. KE' = Ke1' + Ke2' obviously.

problem 2 use the equation for v' for elastic collsions at end of unit schedule to v1' and v2'. Use KE2' goes to PE spring where PE spring = k/2 change in length squared.

Rocket lab due date

Rocket labs will be due Friday. Make preliminary calculations by Thursday so we can see which of the data is any good.They are informal. However you must show how you calculate the J of the rocket motor and see is the difference between h burnout and h top is consistent with the vburn out and free flight after burn out.

remember that gravity is supplying a negative impulse during the burn phase

you can use the vburn out to find the time from burnout to top of flight. see if this consistent with your measurements. You can use v burn out and vtop = 0 to find the average velocity during free flight and use this and time of free flight [ t top - tburn out] to see if htop- hburnout = expected delta h for free flight.

Make it interesting and informative, and make it right.

Canned Food

BRING IT !

After Collision

The prime or apostrophe ' means after the collision.

Rocket labs engine masses

Rocket masses are without engines and the engine masses are : B6-4 19 g; C6-[C6-3 or 5] 24 g; A8-3 16 g.

AP Homework help

1) extra problem sheet #11 ( apologies to Neel)

An 80 kg skater and a 40 kg skater face each other on slippery ice. Without digging in ( i.e. no friction) they push of each other. If the 80 kg skater has a velocity of 3 m/s north what is the 40 kg skater’s velocity?. If the 80 kg skater digs his skates in and pushes horizontally against the ice with a force of 100 to the north for 1.0 seconds while the second skater pushes against him exactly as she did in part (a) what will the 80 skater’s velocity be?

a) 40 kg skater has equla but opposite p so has a v= 6 m/s south

b) impulse from skater A on B = p' from part a= 80 x 3 north now the ice provides a J of 100N x 1 sec to the south so total J on B = 240 north =100 south = 140 pods north so v' in case b = 140/80 m/s = 1.75 m/s north

Honors Homework Help

I wnet through a couple of dozen homeworks from the last week or so.

General comments:

Chapter 16 #41 was done in class

Many of you don't recognize the nature of a problem yet. For example, Chapt 16 problems 44,45, wer Gauss Law problems and should be approached accordingly.

Some of you still think a cm is a meter. If I lend you a penny will you pay me back a dollar? Well cm vs m are the same thing pennies vs dollars a factor of 1/100.

Details:

Honors HW help 11/2 through 11/16
Miscellaneous errors some of you did QT + QS instead of QTxQS in the equation for force between charges

many of you still do not distinguish between cm and meters 1 m squared = 10,000 cm squared so this mistake makes your answers come out very wrong!


Giancoli Chapt 16

# 44 flux = field passing through area = 580 x pi x.18^2 when field is perpendicular to area and flux = 0 when field is parallel to area surface , no field passes through

#45 Use Gauss Law flux = 4 pi Qtotal enclosed
so flux for A1 = 1.13x10^11 x( -1x10^-6 –2x10^-6)

flux =0 for A2

Giancoli Ch 17 [D = delta here ]


Question 5: a point exactly in the middle between two equal positive charges will have zero field since the field from each charge will cancel the other here and only here. The potential is nowhere zero since work would have to be done to bring a positive charge from far away to anywhere near these charges. The zero field point is surrounded by outward pointing fields that you would have to work against to bring a positive charge into this point.

problem #21
DKE = -DPE
when they are very far away from each other PE = 0 KE i = 0 here so KEf = PEi
Mass = 1 mg = 10^-6kg
PEi = kxQsxQT/r = 9x10^9 x 9.5x10^-6 x 9.5x10^-6/ .035

so KEf = 9x10^9 x 9.5x10^-6 x 9.5x10^-6/ .035 = 2.32X10^1 J
v = sqrt( 2KE/Mass) = sqrt (23/10^-6) = 4800 m/s

#70

Ignore capacitance
DV = 35x10^6 Dx = 1500m, so

E = DV/Dx = 23,700 V/m from Gauss: E Area = 4 pi k Qs = 1.13 x10 ^11 xQs

so Qs = E Area /1.13 x10 ^11

Area = 110sq km x10^6 sq m per sq km = 1.11x10^8 m^2

so Qs = 23,700 x1.11x10^8/1.13x10^11 = about 23 Coulombs

Gauss’ Law #2
Flux = E x area = 4 pi kc xQ enclosed by flux surface so Qenclosed = flux/(4 pi x9x10^9) Flux = surface area of box x (-)450 V/meter = [ 2 faces x .2x.2 + 4 faces .4 x.2] = .4 m2 x (-)450 = 180 Q = 180/1.13x10^-11 = 1.59 x10^-9 Coulombs

Giancoli Chapt 7

#7 total p before = total p after

12600 kg car moving at 18 m/s has p (in the horizontal direction) of 12600x18 =226800 pods gravel has no horizontal momentum so p total = 226800 and after the collision the loaded car has a mass of 17950 kg and still a momentum of 226800 so v’ = 226800/mass = 226800/17950= 12.6 m/s

Honors Sect 1 Lab data

Here is the link to your data. See Saturday's post to see what to do with it.

http://h1.ripway.com/DrCherdack/Momentumval%20hnr1.xls

Nick Mak

Please check your email. I sent an important note to you

Honors Project Assignment for Tuesday

Each group has to turn in one summary of what they hope to accomplish on Wednesday during their project group meeting. It should cover how you are to make progress designing your system. Maybe its understand an equation or two, maybe its how to find one of your design quantities

Honors Sect 2 and a few from Section 1

Study Group Reports see blog for October 14. Section 2 must turn them in by this Thursday

All Students

Two items

1) Food Drive begins Wednesday, bring in canned food

2) Anyone interested in an engineering or science program over the summer, here's an announcement from Vanderbilt.

PAVE is a six-week summer course of study designed to strengthen the academic skills of students who are planning to enter a college engineering, pre-medical, science, or technology program. If you are an eleventh grader and planning to take advanced placement or honors mathematics and science courses, the pre-college PAVE program will fortify your senior year and potentially improve your ACT, AP, SAT and TOEFL test scores while increasing your chances for admission when you apply to college. If you are a graduating high school student and are planning to attend any institution, this program not only exposes you to campus life, but also provides you with the experience to overcome the rough spots you may encounter. For more info go to https://pave.vanderbilt.edu/ayindex.php

Email Down Again

Sorry guys, but email is down again so I can't hear you. I'll keep you posted.

Honors PMomentum ( Unit 5) Schedule

Here are your schedule and links for pMomentum in 1 dimension.

http://h1.ripway.com/DrCherdack/HonUnit5-1DMomSched09-10.doc

http://h1.ripway.com/DrCherdack/Unit5Worksheet1r1.doc

http://h1.ripway.com/DrCherdack/Unit5Worksheet2r1.doc

http://h1.ripway.com/DrCherdack/Unit5ProblemSheet.doc

http://h1.ripway.com/DrCherdack/Unit5extraproblemsr1.doc

http://h1.ripway.com/DrCherdack/Collision%20Worksheet%201.doc

http://h1.ripway.com/DrCherdack/Collision%20Worksheet2r1.doc

AP Sect 2 and Honors Sect 2 Lab Data

Here are links to lab data. Note that I have done all the calculations for Honors. AP calculations were done by the students but they still have to calulate percent errors. Note that in many cases percent error is similar for p before = p after and Delta p Wanda = -Detla p Dora, but for both carts having an initial velocity the delta p error is much more reflective of the accuracy of the trial.

Your job is to figure out all the equations used in each column after tb2 and write them out in your lab discussion. Your report is a formal one including error analysis and GOOD conclusions. In addtion, each group must email one spreadsheet to me with the values repaced by the formuale you figured out for the cells after tb2. Because of the extra work, the lab is due Thursday. I expect each group to meet before then.

Gate a is the window gate, gate b is the door side gate. Note that if Wanda is more massive than Dora then Wanda will go through gate b after the collision. If Dora is more massive than Wanda then Wanda should go back through gate a and her velocity' will be negative. In fact any nonzero ta2 reading from gate a will represent a negative v' for Wanda. Wanda may also go back if Dora is about as massive and is moving before the collision.

Also note that if ( and only if) Dora is moving before the collision .025 /tb1 gives her velocity and it is NEGATIVE! and tb2 will give v' for Dora and it is positive.

Also note if you are going to use a cell in a calculation it must be a number only, NO LETTERS.

AP:http://h1.ripway.com/DrCherdack/Momentumvalssect2.xls

Honors: http://h1.ripway.com/DrCherdack/Momentumvalshonsct2.xls

Honors and AP Momentum

Both Honors and AP should read this document and do the sample problems for Mnday

http://h1.ripway.com/DrCherdack/Notes%20on%20MomentumRev1.doc

Honors Assignment

Read Chapter 7 Sections 1,2, and 3. Answer question 1 and think about question 2. Do problems 1,3 and 7

AP Section 2

The scales are still out. What does it take guys?

Honors Assignment

Honors Physics Gauss’ Law Assignment

1. In a neutral beam injector a voltage difference of 500,000 V is created across a gap of .25 m between two large metal plates.

a) What is the field?

b) Assuming that the field is created by a layer of positive charge on a metal plate at one end of the .25m and a layer of negative charge on a similar plate at the other end, how much charge per square meter of plate is required to provide this field?

c) if the injector is designed to accelerate negative deuterium ions (deuterium nuclei being orbited by 2 electrons instead of the usual one) to the right, on which side is the plate with the positive charge?

2. A rectangular box .4 m high and .2 m wide and long has an average field of -450 V/m passing through it surfaces. How much (net) charge does it contain?

Physics/Science League

The schedule for the physics/science league team run by Mr. Gilmore is posted on the fornt baord near the hall door. If you like puzzles and problems, give the league a try.

Centripetal Force Lab

Several of you are making very sloppy assertions about the absence of net force in this lab. There is a net force on the stopper. It is accelerating. The net force is the horizontal component of FT.

There is no net force on the washers. At the washers FT = Mwashers g.

Honors Fusion Power Report

Here is the link AGAIN

http://www.ipp.mpg.de/ippcms/eng/presse/pi/02_06_pi.html

AP 2 lab cleanup

I found five scales out after your clean up efforts and 2 sets of brass weights. I also found weights all over the room and one ramp was carelessly balanced on a box instead of replaced on the rack. In addition, equipment is still being damaged. Therefore all of you who were not still working on the lab after class today have earned -15 points on the torque lab to start with.

We can stop doing labs and just adjust your grades downward by 17 to 20 points or you can learn to care for equipment.

Honors Assignment

Tomorrow is a group research day. Make sure you can use 40 minutes productively. Know enough to start work. Bring in downloads, articles, or books if you need to. Do the following tonight and write a couple of paragraphs about what you learned

1) Plasma group read the two pages on plasma in your text and read the portions that discuss plasma in the European fusion power plant report.
2) heating group go to ITER.org and print out and read the neutral beam injector writeups.
3) magnets read magnetics sections in your text
4) blanket and first wall read about thermal ( heat) conduction in your text and print out and read any blanket sections in European fusion power plant report.
5) thermo group read about thermal ( heat) conduction and thermodynamics in your text
6) electric generators ( dynamos) read about magnetics and Faraday induction in your text

All students: Canned Food Drive

Canned food is being collected in all first period class rooms. These means my AP 1 and topics classes. Other classes: if your first period room is not collecting bring the food to 506.

Show the world you care about other people, bring in plenty of food starting Wednesday Nov 18.

Honors Assignment

Your assignment is as follows,

1) make sure you can do everything on the last test really well ( no peeking if you haven't taken it yet)

2) Do all the flux problems assigned up to now.

3) use a spreadsheet program to prepare a data table for the 50 gram run on your a=F/m lab. If you are in section1, make a scatter chart of a vs 1/mass for the 50 g run and use the linear trendline to find your slope. Make sure you select the display equation option from the trendline dialog box. Compare the slope which = M a with the .49 N force on the system.

AP Labs

Two items Centripetal and Torque Labs

1) Centripetal force lab (5 sub items):

A) friction doesn't change the time reading or speed directly. It does affect what is going on in three possible ways. (1) friction between the string and the top of the tube can reduce the tension at the stopper since now the friction is "absorbing" some of the tension produced by the weight of the washers. (2) A tape rubbing on the top of the tube can produce the aforementioned affect in spades. (3) tape rubbing on the bottom edge of the tube will allow tension in the string above the tape to be higher since some of this tension will be "absorbed" by the friction before reaching the washers to hold them up; i.e. tension at washers is lower than at stopper. Effects 1 and 2 will cause Ms x ac to be lower than Mw x g . Effect 3 will cause the reverse.

B) Measuring radii incorrectly, letting washers swing or orbit, and miscounting rotations are also important sources of error, but can be nearly eliminated by using reasonable care.

C) Since we measure L not r, the vertical component of the string is not important directly. Since r = L cos theta horiz and FT horiz is FT cos theta horiz

FT = Ms omega^2 L cos theta horiz/cos theta horiz = Ms omega^2 L. The real reason for a near horizontal orbit is to reduce the importance of friction vis a vis the other forces by minimizing ratio of normal force between string and top of tube to tension.

D) Some of you have mentioned that Fg is zero. This very very wrong. I assume you meant Fnet on the washers is zero so Ft = Fg on the washers, but this error is so important it still calls for a rewrite. Also note Fg on the stopper in never zero so the tension on the stopper MUST have a vertical component! so that Fnet vertical on the stopper is zero.

E) Fnet on this system as whole is not zero. Part of the system is accelerating with respect to the system, but also with respect to the outside environment. Your hand holding the tube is supplying a net force on the system in the direction of the ac. Think about it. The string is pulling on the tube in the horizontal direction. You are providing a force opposing this. You, in effect are providing the centripetal force. (You are also holding the tube up allowing it to provide the vertical forces canceling the Fgs on the washers and the stopper, yielding no net vertical force on the system.)

2) Torque lab is just fill in but make sure you answer the last question even though it is marked Optional. Also with regard to the questions, we do not use triple beam balances in 506. They are convenient but not trustworthy, not durable. However, most of you still know how they work so answer the question if you can. Lab is due Tuesday.

Email

Email came back on line this afternoon

AP and Email

1) The Bernards BOE Email is still down so I can't "hear" you

2) Here is the Unit 5 Momentum schedule for AP

http://h1.ripway.com/DrCherdack/APUnit5MomntumSched09-10.doc

http://h1.ripway.com/DrCherdack/Unit5Worksheet2r1.doc

http://h1.ripway.com/DrCherdack/Unit5extraproblemsr1.doc

http://h1.ripway.com/DrCherdack/Unit5ProblemSheet.doc

AP and Honors Missing or resubmit Lab update

Two items

1) Here is the latest on labs either missing or requiring correction and resubmission

AP 1: Evan, got your parallel and perpendicular components lab and you did very well on it.

Jay very good work on centripetal force.

Four people still owe centripetal force labs

AP 2: Brian good work on resubmission of components

one centripetal force lab missing. You know who you are.

Honors 1:

Kurt we'll need to go over a=F/m

Sarah, ditto on Conservation of Energy

Missing Electrostatics lab from Amber and Miguel

Hi Carly, you should remember to enter date and period on all labs, just the way Ashley( hi, Ashley) does it.

Honors 2: Jen got your a=F/M and you are done but see my notes. By the way, nice notes on electrostatics.

Missing electrostatics labs from Tony, Maria, Armin, Eric, Dean. Monday is last day!

2) Late homework will receive some partial credit. Enjoy tomorrow but keep plugging and finish your assignments.

3) Cannot check email because I can't reach our server ( again.)

AP and Honors Labs and Assignments

Total of 6 items. Read all the way down to 6 (skip AP or Honors as appropriate)

1) ALL Labs: Here is a link to what labs my records show are overdue to be turned in or are t be resubmitted. If your lab has a grade you want to improve upon, other than what is shown here, I will try to get to it. If you have a lab that is listed as resubmit on it but you are satisfied with the current grade, turn it in anyway with the word STET written on it in large letters. ALL labs where data was complete on last Tuesday will be accepted only on MONDAY. Torque labs not yet completed are due Wednesday. All labs first received after their original due date receive reduced grades depending on how late they are, as do resubmissions that are received more than 6 school days after they were returned to you. However, low grades are still much better than zeroes.

http://h1.ripway.com/DrCherdack/Grades%2011-4-labs091st.xls

2)AP extra credit problems: Do this for homework

http://h1.ripway.com/DrCherdack/APRotMotExtraCred.doc

3) Honors Assignment: Review last test[ DO NOT DOWNLOAD THIS FILE IF YOU HAVE NOT TAKEN THE TEST YET] Here is a link to the test. You may NOT print this out and you must destroy the file after Monday. Your homework is to make sure you can do every problem on this test. Approach it as if you were to take it again on Monday and you need to get 100 on it. [No I did not say I was going to retest you, but act as if I did.] Work with your project/study groups and email me if you are really stuck.

http://h1.ripway.com/DrCherdack/Unit%204ElectrostHnrsquiz2%2009-10.doc

4)AP look for a new unit schedule mid day Sunday.

5) Honors : We will get to Gauss and flux Monday and Tuesday so try your best with the book and notes and homework.

6) See earlier post re bringing lab data for Spreadsheet lessons

AP and Honors

1) For labs next, week we will be working with spreadsheets . On Monday, Honors classes should bring in their a=F/M, acceleration, and Conservation of Energy labs. AP 1 bring in your Moving Cart, a=F/M and centripetal force labs on Tuesday and AP 2 do the same on Thursday.

2) All "see me" and resubmit labs must be in by next Monday. Remember, every lab has a purpose of testing an hypothesis, often expressed as an equation. How well the hypothesis was confirmed should be discussed in your conclusion. All data needed for me to check your results and calculations should be included in the report as well equations used, and preferably at least one sample calculation.

3) Test results were a lot closer to what I feared than to what I hoped.


4)Grade were posted in Home Accident. They do not include yesterday's escapades. Also, for many of you the lab grade was a guess because there are so many outstanding resubmits or missing labs. Many of you should be coming in to discuss your lab status.

AP Sheet R-2 Solutions

For the faint of heart, here are the solutions:

1)rboy =25 xg x1.5/( 33 xg) =1.13 m

2) M2 =24 x 1.5/1.25 = 28.8 kg

3)M2 g= (-20 g x 0.5+25 g x 1.0)/ 1.75 or M2 = 8 kg

4) take torque around east pier Fwest = (7.5x10^6 x100m + 5x10^6 x150m)/200m = 8.25x10^6N
Feast total weight - Fwest = 13.5x10^6 - 8.25x10^6N = 5.25x10^6

5) FT cos 30 = 500Nx.8m/1.6m =250 N FT = 250/cos30 = 288N

Honors Homework

Try to get Gauss' Law and flux homework in by Wednesday morning or after school Wednesday. Spend tonight studying. Make sure you know the ideas from last week's quiz and how to apply them. Know the difference and relations between fields and forces and voltage and PE.

AP Advanced Study assignment

Complete the advanced study assignment for the torque lab by Tuesday

AP Unit 3 retest

I f you scored below 78 on the Unit 3 test you can take a retest any time between after school on Tuesday and 3:30 on Wednesday ( that's the finish time not the start.)

All AP Components Labs

I have nearly finished grading the Section 2 labs and most of them are awful, however much of this applies to reports from both classes. Many have no data on the hanging mass used to find Fg// or the reading of FN using the scale. The purpose of the lab is to see if using Fg cos theta vertical for Fg// and Fg cos theta horiz for Fgperp works. How are you to compare your calculated values to the real values if you do not record or show the real values? Just because you did not receive a nice, pre-made data table which had blanks for you to fill in, doesn't mean you were not responsible for recording data.

Some of you continue to leave out the calculations you made to find values. You must include at least the equations you used and all the data used to arrive at your predicted or expected or ideal values and your value calculated from measurements. For example Fg// predicted = Mcartg x h/L and Fg// actual = Mhanging x g.

Many of you used the cos, h/L, to find the angle using cos^-1 on your calculator. You then found the cos from cos of the theta you found from the cos^-1. This shows a level of incomprehension that is alarming. You found the angle from the cos and then found the cos from this angle. I guess you have a lot of time to waste. [By the way, you should know that a^-1 x a = 1 ]. You didn't need to find the angles since h/L = cos theta vertical and b/L = cos theta horizontal [or use 1- (cos theta v) ^2 = (cos theta h) ^2]. Your depedence on your claulators for finding everything is scary.

Many of you talk about the spring scale not giving an accurate reading for Fg//. Well, we didn't use spring scales for Fg// did we? We used hanging masses and they gave very accurate readings as long as you counted the masses properly and didn't have anything jamming your pulleys.

You will have until next Monday, 11/9 to correct these disasters, but this will be the last lab for which I will allow this kind of resubmission. Many of you will have to re do the lab this week becuase of your failure to record the data.

AP and Honors Quizzes

We will be having substantial quizzes on Teuesday. AP quiz will include up to torque.

Honors quiz will include all we have done on force and motion, work and energy up to, but not including flux and Gauss'Law. Ask me how the test will be scored vis a vis last test in class.

AP

For tonight, also:Calculate the orbit radius for a geosynchronous orbit and the speed (m /s and mph)

Honors Test Important

If you had a test with a number greater than 20 and MC #6 was marked as wrong, see me. It may pay you to do so.

F/m and PE gravitational

Some students tried to find acceleration by dividing Fnet by meters traveled instead of mass. This despite a few labs on the subject.

Many of you didn't even bother with Fnet and chose whatever force popped into your mind first either Mg or Frope. Only a few found the sum of Frope + -Mg

Most of you also decided that even though the elevator rose, it lost PE.

Important to all students KE and PE

Delta KE =-Delta PE only when there is no net work done by or on the system. A more complete statement of energy conservation is for a system.

Win + Heat in= Delta PE + Delta KE + Delta U ( change in thermal energy)

This should be well known to those doing energy readings.

. In fact you should all read this latest, hot off the press, revision. This will give you AP students a leg up on future work. If you do not have time now make sure you note the post and comeback to it. Honors and Topics folks, read it now.

http://h1.ripway.com/DrCherdack/Notes%20%20Work%20and%20Energy%20R5.doc

Fnet is not MG unless gravity is the lone force on the object.

Fnet is not mg if there are forces like ropes or normal forces acting on an object. I had no idea why, when you are told a rope is pulling a bucket up with a force of 105 N, you can say the net force on the bucket is Mg, but I think see the problem now. You think a and - g are interchangeable. a =-g is only true in free fall when gravity is the only force. Too many FORMULAS, too little understanding. Clearly you still do not know that Fnet is the vector sum of the forces on an object even when this fact is printed at the beginning of your test, or you do not understand that things that have forces on them other than gravity do not accelerate at -g. By now you should have noticed that not everything on earth is accelerating downward at -g. Since this course is about the real world and the real world is full of objects not in free fall you do, now , I hope, realize that a does not = -g in general and certainly not when a rope is pulling upward with a force greater than Mg.

Mass vs Charge

The number of students in my honors class who did not distinguish between charge and mass is very alarming. Mass of a proton = 1.67^-27 kg as does mass of a neutron. Charge of neutron is, you guessed it, zero. Charge of a proton is 1.6x10^-19 Coulombs. Its time to start understanding that these symbols, Q and M, are real physical quantities. By now you must know that electric fields act on electric charges through F = Q Efield and that

a=Fnet /mass not /charge. Do not make these errors again.

Honors Unit 4 Schedule

Here is the schedule for our new unit on electric forces fields and potential

http://h1.ripway.com/DrCherdack/HonorsUnit4SchedA.doc

AP Unit 4 Assignments

Here is your Unit 4 material

http://h1.ripway.com/DrCherdack/APUnit4schedrotmot09-10.doc

http://h1.ripway.com/DrCherdack/Unit4AP-09-10ProbSh.doc

http://h1.ripway.com/DrCherdack/planets%20or%20Satellites%20in%20Orbit.doc

http://h1.ripway.com/DrCherdack/NotesonTorque%20rev%2012-30.doc
http://h1.ripway.com/DrCherdack/PlanetWS.xls

http://h1.ripway.com/DrCherdack/ProblemSheetR-1rev1.doc

http://h1.ripway.com/DrCherdack/ProblemSheetR-2.doc

http://h1.ripway.com/DrCherdack/Problem%20Sheet%20R-3A.doc

Assignments

Please try the oncourse links one more time. They may have gotten some of the bugs out. Let me know if you still cannot download. In the mean time I will post them on my usual server in the evening. Check back here around 7:30.

Lab Link

It looks like my file storage server is back up. Here is one for our next AP Lab. Look it over and print it out. The trouble may have been malware infecting the 506 desktop. It did have 15 infected files. It has been cleaned up, but I'll try to do my uploads from home which seems to be safer.

http://h1.ripway.com/DrCherdack/CentripetalForce08-9.doc

Honors and AP schedules

Schedules are now posted on homework and events October 23. Note on AP schedule the planet worksheet is the file named SolarSystem.xls

Honors Schedule

I have developed a schedule of our new unit: Unit 4 Electric Forces, Fields, and Potential. Unfortunately Off course is busy upgrading its document features so it won't allow me to upload the schedule. At least when they are done I may be able to see my documents in alphabetical or chronological order. Right now it displays them randomly; not too useful when you've got a couple of hundred documents to search through.

AP Assignment

Do Assignment 3 on Mastering Physics. New Unit Schedule will be posted soon

Honors Assignment

Re read Chapt 16 Sections 1 through 5 and Notes on Electrostatics. You really need to do this! There may be a quick quiz to ensure you do. Do Questions 1,8 Problems 3,5, 25 (use F=QE in reverse) A new schedule for unit 4 will be posted soon

AP Assignment

My first upload of the rotational motion definitions got corrupted either by viruses on my laptop or our network or by Oncourse. The new upload works so things should be okay for now.

AP Assignment

For tonight Read Definitions for Rotational Motion pages 1 and 2 posted as tonights' assignment on homework and events Also read Chapt 6 Sect 1 and 2 . Do conceptual questions 1,3, and 9 and problems 1 and 7.

Interesting Physics and Astronomy events

This is from Bergen County College, about 50 minutes away in Paramus ( the home of campmor for you outdoor types and 4 big malls for the shopaholics).

Our Astronomy Lecture series continues and we hope that you will be able
to attend our October 29 talk given by Dr. Steele Hill about the SOHO
Solar Observation mission and/or our November 5th presentation by Dr.
Jim Gates on Supersymmetry and CERN. Both talks will start at 12:30 pm
in our Technology Building room TEC-128.
(http://www.bergen.edu/images/pr/campusmap-10-07.gif). Directions to the
campus are at http://www.bergen.edu/pages/1690.asp. We encourage you to
urge your students (high school and college) to attend as our speakers
are eager to have them at the talks. Therefore, I am urging you

Honors Assignment

Despite telling me the assignment is posted and showing it to me in my view, Offcourse systems won't let you see it in the public view. They are protecting you from seeing an assignment a day before it is due. The reason I did not post it Tuesday, today, was because the notes I wrote for the AP assignment would then also appear with the Honors assignment and I did not want to confuse you. I forgot about this wonderful feature of Offcourse. I am sure there is a way to work around all of this and I just can't wait to spend the oodles of spare time I have just learning what it is.

You can see why I preferred my private free file storage service to Offcourse which the school system pays for.

Honors WS2

The worksheet is now posted on Oct 21 in homework and events. Don't just not try. Use all you've learned to figure out how to do it. Sometimes something is missing, but you can find that something from the information you have and the physics relationships we have studied.

Honors: The Conservation of Energy Lab

Lab is a mini but have a good discussion of energy conservation, i.e. PE lost is KE gained. and make sure you compare the two not just say they are the same. Consider % difference. This is found from

(- delta PE - Delta KE)/(-Delta PE) x 100 (to get percent)

I'd say anything less than about 8 % was pretty good although I've seen some in the 1 % range in the past.

Note the last column should be - delta PE since delta PE is a negative number and you want subtract the KE from a positive number.

Assignments Again

Current Honors Schedules and workshhets can be found on events and homework posted Oct 15 and 16th and see some notes posted on the 12 th ( ignore the schedule posted on the 12th). Current AP schedule and worksheet are posted on Oct 19th.

Assignments and Schedules

I am posting schedules and materials on the homework and events pages of my website. Do the homework as called for in the unit schedules and on this blog. the fact that an assignment is posted on a particular day does not mean it is due that day. Nor does it mean its all that is due that day.

AP assignments

Unit 3 schedule and WS 3 are now posted on homework and events Oct 19

Honors Labs

Many of the lab on acceleration reports had the same old problem. You used the same data to form and confirm the equation. You need to test an equation against quantities derived independently of the equation you are seeking to confirm.

Consider the questions I asked you.


I asked you what the mass was. I asked you what the force was. What can you find from this information?


Next I asked you did the slope of the graph confirm a kinematic equation. Many of you said sure the slope = 2 a and then proceded to prove by showing how 2a = vf squared/delta x. This is not a laboratory proof it is a restatement of our theory. Then you calculated the slope and said it sure equaled 2a ( some actually dropped the 2 and said it equalled a) by comparing it with the a you found from the very graph the slope came from. This proves nothing except you can get the same answer from the same numbers. You must compare the a found from the slope to a from some other way of finding a. Now think about the first two questions above and if they offer another and independent way calculate a. Now if that other a and 1/2 the slope are equal, you can confirm the validity of our kinematics equation. Remember, this is physics. If nature does not confirm it, it isn't right.

Honors Labs

The accleration lab reports were mostly pretty good. However, there is still some sloppiness in wording. Many of you said that the velocity increases as the distance. While it is true that the velocity does increase when the distance increases, the phrase increases as means proportional to. i.e. if a increases as b then a = constant x b. Therefore it is v squared that increases as distance not v. This is crucial to the meaning of the lab which is meant to confirm one of our kinematice equations but more importantly, to lead you to the concept that force exerted over a distance changes energy.

A=F/m lab Revisited

Nearly all the labs from AP Section 1 and many from AP Section 2 have to be redone. You had to find Ma from the slope of the graph and Force from Mhanging x g and compare them. Most of you simply said Ma = force. Some of you compared your slope to the slopes for point on the graph. This produced the not very startling fact that the slope = the slope. However you thought it proved slope = force. F =Ma is not to be assumed. It is the hypothesis we were testing!!! go back and reread the post from October 10th and do the lab right.

Honors Force, Motion, and Energy WS 1

The WS is now posted as an assignment on Friday 10/16 on Homework and Events on my website.

Topics in Physics

Proposals for your report/presentations are due Monday. A proposal must include an outline of what you will cover including key physics and what relationships you expect to derive/explain/describe e.g dependence of flame speed on reaction energy and mixture density.

Honors Groups

Remember that each group must have met by Thursday for the Force, Motion, and Energy unit and each student must report on who, where, when and what was covered
but

EVEN MORE IMPORTANTLY by Monday each group should have prepared a brief outline including the system function and what important features of their system they will discuss (list several) and what key quantities they will produce such as nuclei per m3 and temperature for plasma; type and number of particles per sec for heating; field strengths etc. for magnets; vessel material and thicknesses for first wall and blanket; working fluid and flow rates for thermo; and currents for generator.

Make use of the fusion power plant study link I posted and the system issues I posted here earlier.

For more information ( you don't need to do much of this by Monday), look for links to (try the ITER site for some good stuff on these first three systems)
fusion plasmas, plasma confinement, transport in plasmas (probably much too much info here)
neutral beam heating and RF plasma heating,
tokamak magnets superconductors for magnets, tritium breeding and fusion reactor blankets, information on Rankine cycles, steam generators and steam turbines, helium brayton cycles if you choose a helium instead of steam cycle,
electric generators, power plant gnerators, large AC generators

Blog Links

My file storage site is still not working so assignments and notes will be posted at my oncourse website homework and events page.

However, keep checking the blog for other news.

Honors Energy Conservation Lab

Make sure your results for energy are in Joules so everything needs to be in m and kg. Remember work is force times distance and in this case your work in lifting cylinder is giving it potential energy. Note that as the cylinder the . This potential energy is then being converted into KE on the wasy down. So the change in PE is negative and the change in KE is positive, but they should be equal amounts.

If you are having difficulties, give it a good shot, but we will go over it on Monday. Since the report is not due til Tuesday for Section 2 you should have enough time to write your report.

AP Section 2 (4th period)

Please remember the homework problems for which you needed help so we can go over them tomorrow. Today's shortened periods coupled with you folks taking a while to do the lab prevented homework review today.

All Students: Links

Links to the server where I usually store my documents are not working at the moment so please look for assignments on my Oncourse website homework and events page.

Do keep checking the blog for news, comments, lab hints, etc.

Honors Notes on Electrostatics

Please destroy the version with the extraneous material on it and use version R1, now available on my oncourse website events page.

Honors Links

You're right folks the links don't work right now so I posted the schedule and notes on the events page on my website at oncourse

Honors Unit 3 Schedule

Here is the schedule for our study of force, motion, and energy.

The notes should prove useful. Although we will do potential more in the next unit, it will pay you to read them now.


http://h1.ripway.com/DrCherdack/HnrsUnit3SchedR1.doc

http://h1.ripway.com/DrCherdack/NotesElectrostatic3-08r1.doc

Honors Assignment

Read Sections 6.1 through 6-3. Do Chapter 6 problems 1,2,3

All Students Group Meeting Reports

Every student is to participate in at least one group meeting per unit outside of class hours.

EACH student is to submit an individual report ( not a group report) before the test for that unit, The report shall state who, when, where; and what was studied .

Honors students will begin this with this unit.

AP students are to meet once again for this unit and report on it.

All Students

The server where I load my assignments is having a problem, so go to the assignemnts events section of my website for the Unit 3 schedule and some notes you'll need

Honors

Bring in all your labs tomorrow. We will spend the day learning, I hope, how to describe, interpret, and draw conclusions from what we observe.

a=F/Mass Lab

I just finished grading one section. The vast majority of you said that indeed F= Ma or a=F/M. Unfortunately only a small minority bothered to support their conclusion with calculations. This is NOT GOOD ENOUGH. You must learn to go beyond doing the absolute minimum of what you are told. I asked you to support your conclusion. Some of you said the the acceleration went down as the mass went up. This is still NOT good enough. This would be true if M = Msquared times a cubed or square root of M times cube root of a, etc. You are to make calculations to demonstrate your conclusion. Why do you think I asked you to plot a vs 1/mass. Haven't we used the slope to find relationships from assemblies of data points? Isn't the slope of your plot Ma? Is is not something you can compare with the force ( hanging mass x g) to tell quickly whether or not Ma =F?

Some of you compared Ma with F for each run. This is fine, but using the slope tends to cancel out random errors that occur in individual trials in most labs.

Some of you had bad data that came from ignoring warnings about checking the photo gate heights to make sure only the top band was blocking the light in the gate. This was particularly true on the last trials, where the third bar tends to interfere with the gate light. You should know that where you measured tiny , or even negative accelerations, its because the second gate was reading some length different from what the first gate read. Similarly, an unexpectedly large acceleration should tip you off that you read a greater length in gate 1 than in gate 2. A glance at the data should tell you where you went wrong. For example a doubling of t from the previous run where you expected a 25% increase is a tip off.

AP Ferryman Lab

Most lab reports were pretty good. However many of you persist in the use of triangles in inappropriate ways. Try to outgrow triangles and think in terms of vectors and components. When drawing vector additions or triangles some of you seem to be incapable of placing the base at the top. In the ferryman Part 2 it seems natural to place the 30. m length at the top since it is the displacement along the north shore, but many of you drew it at the bottom and thus had the boat either going northwest or southeast graphically when it was of course going northeast.

Part 3: Some of you are still ignoring the process of finding relative velocity. You just assume that the 20 m/s vboat,water is a leg and the river current is another leg and you get a wrong right triangle. You need to use the idea that vboat, shore = vboat,water + vwater,shore and recognize that vboat,shore( the sum or resultant) must have zero x component. This leads to vboat,water's x component must = -vwater,shore ( also known as the current). In this case the addition of a diagonal vector ( one with north and east components) and an - east only vector ( the current) is a North only vector.

AP Quiz

Yes, we will have a quiz Tuesday, but it will really be a quiz, about 1/2 a period worth or less.

Honors Unit 3 Schedule

Here is the beginning of your new schedule using our brand new books. A more complete schedule will be available soon.

http://h1.ripway.com/DrCherdack/HnrsUnit3SechedPt1.doc

http://h1.ripway.com/DrCherdack/NotesWorkandEnergyR3.doc

All Students Homework

I have been looking at the homeworks, especially those that need help. YOU MUST IDENTIFY THE ASSIGNMENT. Worksheet number, Chapter and problem, due date all should be clearly identified.

Also, write down at least enough information so the nature of the question and your approach are clear. Much of what I see is worthless from the point of studying from and impossible for me to assess if you are doing things right because its disconnected scraps of information. Organizing your work o0n these problkems will go along way to organizing your thinking and improving your understanding.

AP Forces Unit 3

Finally, here it is, unlovely perhaps, but better than nothing:

http://h1.ripway.com/DrCherdack/APunit3sched%2009-10.doc

http://h1.ripway.com/DrCherdack/Unit_3_Worksheet_2r1.doc

http://h1.ripway.com/DrCherdack/Unit_3_Worksheet_3.doc

Honors 6th period

I think I may have said some things that scared some of you. When I quickly went through the three equations that can be derived relating displacement, velocity, acceleration and time, I did not mean to imply that I expected you to be fully familiar with them by Friday.

I wanted to show you how understanding a few simple ideas like displacement equalling time x average velocity and acceleration equalling change in velocity/ time could allow one to analyze and predict motion pretty completely. This was a preview of what will come in the course of our studies of motion and we will go over these equations more than once in the future. It is much more important that you see and understand where they come from then to memorize them and endlessly practice using them.

In the mean time, just knowing the definitions of average velocity and acceleration, and that vavg =(vi+vf)/2 and that vf = vi + aDt should suffice. You can use this information a bit at a time to solve problems without joining them up into more complex equations.

Honors Assignment

1) Identify which fundamental force is associated with;
Friction,
normal forces,
objects falling
planets in orbit,
ions circling in plasma

2) A mass of 14 kg is pulled with a net force of 42 Newtons north. What is its acceleration? If it starts from rest how fast is it moving after 3 seconds?. What was its average velocity during the 3 seconds? How far did it go?

3) What is the force on a tritium nucleus moving at 2 x10 6 m/s in magnetic field of 3 Tesla. What is the resulting acceleration? Does it make the tritium go faster or just change its direction to make it go in a circle?

AP Assignment

Almost finished with your schedule but not yet. Here is tonight's bundle of joy:

Read 5.1 through 5.3 Unit 3 WS-1 prob 1and 3 prob 5 with no friction

Unit 3 Problem Sheet 1,2,3,4

Save extra problems for the near future

http://h1.ripway.com/DrCherdack/Unit3problemsheet.doc

http://h1.ripway.com/DrCherdack/unit_3_extraproblemsR2.doc

Honors Quiz

Yep, it'll be Friday since we still need to do some review. I'll get some problems that address what you should have learned about 1 D motion up in a little while so stay tuned.

Honors Reminder

You must choose your power plant system by Friday

More on a =F/m

Plotting the graphs:
as for the horizontal axis where the quantity is 1/mass just do it the normal way you would for any quantity. You should start the scale at zero and it goes to about 2 (1/kg). Place the values where they belong on this scale . For example if a data point has a 1/mass = .67 it goes one third of the way from the origin to the 2 (1/kg) mark ( 2/3 is 1/3 of the way from 0 to 2).

We want a straight diagonal line increasing upward from left to right.

Honors Assignment

Try these for tonight and then we'll get back to kinematics.

Honors Unit 2 Force Work Sheet 09-2

1. A car is accelerating at 3 m/s2 to the north. If the car’s mass is 1500kg what is the net force acting on it?

2. A spring is stretched so that it produces a force of 20 N. How fast will it accelerate a 0.5 kg mass? Will the acceleration increase, decrease, or remain the same as the spring becomes less stretched?

3. A deuterium nucleus is placed in a magnetic field, B, with a strength of 4 Tesla. If the deuterium is moving at 2x106 m/s, what is its acceleration due to the field. [Reminder F=qv x B]

4. List the forces and their directions for a child going down a slide. Think about the two forces the slide produces and describe the role they play in the motion.

Lab Resubmits

Resubmits are due with in 5 days of your receiving them. I am rapidly approaching the point where I will no longer allow resubmits for poor use of graphs, not knowing what slope etc. means, and just plain sloppiness with regard to what acceleration, velocity, and dipalcement mean and how they relate.

Labs on a =F/m

Make sure you address the title question in your purpose, discussions, and conclusions. You must justify your conclusion. Think about using the slope to do so. Make sure you plot a vs 1/mass.

AP classes print your lab sheets for use in class.

Formal again and make sure you follow course guide.

AP Assignment

DO MC 24,25 problems 30 ,35, 41, 53, 67 (before it leaves the ground!)

Do Unit 3 WS-1 for problems 1 and 5 just draw the free body diagrams. For problem 5 identify the internal and external forces, considering the system to be the two masses and the rope between them.

http://h1.ripway.com/DrCherdack/Unit_3_Worksheet_1.doc

Corrected Honors Schedule

Here is a corrected schedule. By the way books should be in next week.

http://h1.ripway.com/DrCherdack/Hon%20Unit_2_Sched09-10-1.doc

AP Assignment

Read chapter 4 complete ( not much to do if you read already up to 122 as you should have )

Do conceptuals 17,19 MCs 21,22 probs 19,21 23,61

Read lab at link below

http://h1.ripway.com/DrCherdack/Lab%20on%20a%20=F%20divided%20bym%20AP.doc

Honors Assignment

Try this for tonight

http://h1.ripway.com/DrCherdack/Hnrs%20Unit21-DWS3-09.doc

For All Use words carefully

Many labs are plagued with sloppy writing of your thoughts or writing that reflects sloppy thinking. Words have meaning: the velocity is not the same as the rate of increase of velocity. Many of you say the acceleration is increasing when you should mean the acceleration is positive or non zero. Some of you have told me it is the acceleration that is increasing because the velocity is constant.



If the displacement is increasing at a constant rate then the velocity is not increasing, it is remaining constant.

If the velocity is increasing at a constant rate, it is the velocity that is increasing while the acceleration is constant. If the velocity is increasing at a constant rate, then the rate of increase of displacement is increasing. Note the double increase in this last phrase here.

Honors Fusion Power Plant Project Groups

By Friday of this week, you will need to have selected which portion of the plant you want to study in detail and for which you will come up with designs. I would like to have between 3 and 4 people per team, certainly no more than 4. E mail me as soon as you have made up your mind. Rank all 6 systems in order of preference and let me know which ones you really feel strongly about. I will try my best to give you your first or second choice but we will need a complete plant or we'll produce no power.

I have included some of what you will learn and some of what you will end up calculating or selecting. DON'T PANIC: you've got lots of time to learn about this stuff; after all your very final reports are due in June. The link to the European fusion power plant report I posted will provide you with a great resource. I will also provide many additional references as needed. YOU WILL NOT BE ALONE.

The plant systems are

1) Plasma including temperature, particle density, size, heating needs. This group will learn about plasmas fuse, how particles leave plasmas, and a little bit about waves in plasmas.

2) Heating using neutral beams and electromagnetic waves including ionization and neutralization methods, voltages, currents for neutral beams and frequencies and wave lengths for electromagnetic waves. This group will learn a lot about electric forces and microwaves.

3) Magnets for confinement ( and some heating) including toroidal, poloidal and ohmic heating coils, their purposes, the current required materials used and forces they generate right in the magnet itself. This group will learn details about the relationships between currents, magnetic fields, and forces; what it takes to resist forces. They will also learn about superconductors.

4) First wall and blankets to protect plasma from outside world, breed tritium, and protect magnets from heat and neutrons. Also must be compatible with the cooling system. materials, amounts, operating temperatures, strengths required will all be addressed here. This group will learn about materials strengths, resistant to heat, neutron absorption, heat transfer, and how to make a vessel strong enough.

5) Thermodynamic system to cool the lithium, produce steam and use the steam to drive a turbine at 60 ( or perhaps just 30) rotations per second. This group will learn about thermodynamics, transfer of heat, and the mechanics of using high speed steam to push a turbine blade. Key parameters to be determined are temperatures and pressures throughout the system and flow rates of steam required, and surfaces areas needed for heat transfer. ( If you like to cook, maybe this ones for you)

6) Electric generator to convert the mechanical energy from the turbine into electrical energy. This group will learn about how to create magnetic fields using current and then using these magnetic fields to generate much larger currents. The field strengths areas of coils, numbers of turns, operating voltages and currents are all key outputs from this group.

All students

Always keep in mind what you are doing. For example many students found the x component of a position and the y component of a position and the hypotenuse for that position which is fine. Then many of you used this to find the angle using you calculator's inverse cos or inverse sin functions and compared it with the angle measured by protractor. This is also fine although you should keep in mind which measurement, say 19 cm with a precision of 1/10 cm or degrees with a precision of a degree or two, is more accurate.

However some of you used the angle from inverse cos and inverse sin and then used that angle to find cos and sin again. This is circular reasoning. Starting with cos and using it to find the angle and then finding cos of that angle is just wasting time and demonstrating that you don't really know what the cos means.

Again, think about what your are doing and understand why you are doing it. DO NOT REDUCE THINGS TO BLINDLY FOLLOWING PROCEDURES AND USING FORMULAE.

Labs

Remember that our labs are part of the scientific method. All ( or nearly all) our labs have a purpose of confirming the theory we have established from observation, deduction , and some algebra. The projectile motion lab's purpose was to confirm our projectile motion equations relating v,delta t, a, delta x and delta y. This includes the fact that the y and x motions are independent except through a common time of flight.

The a =F/m? lab's purpose is contained in its title.

Your conclusion section should reflect the purpose of the lab. It should state whether or not the experiment confirms our theory and include a summary of the supporting evidence for your conclusion. This is the final step of the scientific method: reporting on the results of testing your hypothesis.

Note that if you use 3 different equations applied to two differing kinds of motion and your results come within 5 % of your prediction, it probably indicates your theory is pretty good. This is especially true if your equipment and measuring techniques are not perfect.

Honors Assignment

Complete sheet FS-1. Note that the force of gravity = 10 N/kg. ALso not that if there is no acceleration, it must mean that all the forces cancel each other out. For example a lamp hanging from a chain has a force from gravity pulling it down, but an equally strong force from the chain pulling it up.

Note that zero net force means no acceleration, but the object can still be moving with a constant velocity, it doesn't have to stand still.

AP Assignment

For Monday Read pages 105 through 122. Do Conceptual Questions 1,3, 7 and problems 1, 7, 11 ( show diagrams for 7 and 11) 13,15 . Assume rubber bands are identical.

Labs

The AP ferryman and the Honors a =F/m lab are both formal. Focus on the discussion, keep the purpose of the lab in mind both for the discussion and conclusion sections. In the ferryman we want to demonstrate our methods of finding and using components is correct as well as our way of adding velocities to find relative velocity. In the other lab the purpose is answering the quesion in the title. Make sure you do answer it.

All Students

You have no idea how rewarding and gratifying it is to create a second test for a unit , stay to administer a second test, rush to grade a second test so you can get the results right away, and then have the tests sit in the out folder because you cannot be bothered to look in the out folder.

This applies to labs and homeworks as well, so
LOOK IN THE OUT FOLDER EVERY DAY

All students

DO NOT WRITE ON TESTS...I am trying to cut down on wasted photo copying. so once again.

DO NOT WRITE ON TESTS points will be taken off next time

read this to yourself 50 times

AP Ferry Boat Lab

Make it a brief formal lab due Thursday for Section 1. Include all the trig with brief discussion of why what you did worked. Procedure can be pretty minimal. Focus on the idea of adding boat wrt to water + water wrt shore to get boat wrt shore and how you used components and trig.

Honors Free Fall Lab

The velocity vs time graph should be a straight line and so it is its own tangent. I wanted you all to realize this and to think about the fact that your velocity graph had a constant slope and what this means about the acceleration. The velocity graph should cross the vertical axis a bit above zero since the weight was already in motion at what you used as your zeroth data ( length = 0) point. In other words you started using data a few intervals into the free fall; you did not start using data from the very beginning of the fall, so the velocity at your zeroth length point was already greater than zero. Hope this helps and next time do the lab sooner, while it is all fresh.

AP Retest

I just finished writing the test. Some of the questions are very different from the original, not harder, but different. Be sure you know the definitions of a and of vavg and how to use them to find delta t and to find delta x. Also be sure you know how to use the displacement = vf^2 -vi^2/2a to find vf or to find a.