Everyone

Well, I was going to start this note with some remarks about some lab reports, but I thought it might be better to let that wait.

So instead:

I hope you have a very Happy New Year with lots of joy and success - especially when it comes to physics.

Everyone

1) The attendance today was very disappointing. It reflects an attitude toward our class that I am sorry to see. To those who did attend class, thanks. I hope you enjoyed and benefited from it.

2) Break Assignment. AP you already have yours.

Honors: Here it is. Counts as 4 homeworks. Present answers on clean sheets not the assignment. Show work for problems. Problems can count as a take home test for you if you declare it so. You can use notes, texts, and even help each other but you must understand what you did. I will question at least some of you and if I believe you just copied I will disallow the test for everyone.


http://h1.ripway.com/DrCherdack/December%20Assign.doc

3) Honors projects: Be prepared to present at least one forty minute class on your topic by January 3rd. A second presentation and written report covering all items in your outline will be required by January 11.

4) We raised about $430 for the Smile Train. Nice work everyone.

5) Enjoy your holidays, be kind to your friends and relations and do something good for strangers. See you next year.

Simple Harmonic Part 3 data

If your part 3 data was poor and led to ks much different from parts 1 and 2, use these data

Amplitude m Time of card through gate Velocity max m/s

.05_________ .103_________________ .1844

.1 __________.051__________________ .3725

.15________ .033 _____________________.5758

.2 __________.025 ____________________.76

.25 ___________.020 __________________.95

Physics Tee Shirts

Get your orders in tomorrow for the shirt of the decade - The Ridge Physics Tee shirt.

Check payable to Ridge Activities - Physics or cash.

Follow the link to see it in full color and print an order form. (You don't need the order form; any paper with your name, size and teacher's name will do)

http://h1.ripway.com/DrCherdack/PHYSICS%20TEE%20SHIRT.doc

Charity Jar

Today's donations were pretty thing except for continued outstanding generosity from Joey. Let's dig in and make a real difference in some kids life.

AP Break Assignment

Your Break Assignment is in the out folders. It comprises three parts : a set of ten problems ( if I counted correctly - don't laugh, it could happen) -do not write on this; a graph for completing question1 - you can write on this; a set of equations for your use throughout the rest of the course.

The assignment will count as five homeworks. Problems are to be solved on clean sheets with all work shown. Booklets are to be kept clean and unmarked.

All Classes Units

I found lots of errors in choosing units, especially in the Simple Harmonics Lab (AP you'll be doing this soon enough).
The dimensions of a quantity are easily found. For example k is used in

Force (N) = k* displacement (m). Since k* (m) = N k must have units of (N/m).

Newtons are also (kg m/s^2) so k also has the units of (kg/s^2)

A graph of period squared vs Mass has a slope with units of time squared/mass or (s^2/kg)

A graph of v vs Amplitude must have a slope of (m/s)/(m) = (/s).

In another lab I asked what the units of energy /mass were, these are ( kg m^2/s^2)/kg =m^2/s^2

Pendulum Lab

We spent a precious period seeing that pendulum motion has an acceleration proportional to the displacement from equilibrium, so the motion should be harmonic.,and for a pendulum omega squared =g/L or omega =. Your lab was supposed to demonstrate that T ( which you measured) should equal 2 pi/sqrt(g/L) , your expected value of T based on our hypothesis about omega = restoring acceleration/displacement.

Power Lab

I am still getting in labs that miss the main point, viz. that power increases with decreasing time to perform the work. While the KE did increase with reduced time as speed has to increase, the real major effect comes from the change in PE, which is much larger than the KE, comes about in a shorter time.

Tis the Season

Remember the collection jar in 506 and always think of helping others.

Archimedes Lab

I am concerned that many of you will soon, if not already, confuse the reading of the scale with the object submerged with the mass of the beaker+ mass water + mass of object. This is NOT the case.

the reading of the scale with the object submerged IS the mass of the beaker+ mass water + the force of the object on the water. This last quantity, the force of the object on the water, is the buoyant force.(except it's down where Fb is up)

Labs

1) The Rotational and Translational KE lab asked two questions that received a large number of incorrect answers.

1) Would the velocity be affected if the mass of the ball changed. The correct answer is no, because both the KE and PE are proportional to the mass so that increasing the mass would increase the PE converted to KE sufficiently to keep v the same, or in equations

.7M vfinal^2 = Mg h initial

3) What would be the velocity if the ball just slid without friction instead of rolled. Since the final KE would still equal the initial PE we have PEi =.7Mvroll^2 = 0.5Mvslide^2

so vslide^2 = .7/.5 vroll^2 or

vslide = sqrt(.7/.5) vroll

Honors Test

Section 2 please return your tests. I need to correct one of he answers.

Honors Projects

Your assignment for the tonight and the weekend is to produce a detailed outline of what you will present to the class and in a report. The outline must include addressing the subtopics I indicated for your area. One outline per group.

Labs will be a real plus, demos are also important. Contact me immediately with any needs in this regard.

It should be annotated with sources.

In must be in on Monday. It will be graded.

AP Problem Sheet for Fluids

Here it is, no excuse for not doing it now.

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

Governor's Schools Science and Engineering

Governor's schools are opportunities to study science or engineering at the college level this summer. A good way to learn and also looks good on applications, for those few of you thinking of going to college.

Read about them on Miss Donlevie's website.

Food Drive last Day

We need a really big push for this. We are still about 20 bags short of what we should be doing.

AP Section 5

Please return your tests to me. I made an error in my answer sheet and you may be getting a few more points, and we both know you can use them.

Tee Shirts

Due to popular demand ( Irwin Popular demanded it) tee shirt orders will be accepted until Thursday 12/16 This probably kills Christmas delivery but they will make great Valentines gifts (don't quote me).

Food Drive

You've got the weekend to purchase food and bring it in on Monday. We are still way short of one bag per person and the drive ends Wednesday

Honors Schedule

Here is the schedule for the remainder of harmonic oscillations. Note the quiz on Thursday.



http://h1.ripway.com/DrCherdack/unit9worksheet1r1RNC.doc


http://h1.ripway.com/DrCherdack/HonUnit7sched10-11.doc

Lab Cleanup

Lab cleanups have been nearly nonexistent. The lack of care and courtesy shown by you has been appalling. For example, I have just put away all but one of the springs from the harmonics lab. Stopwatches are all over the room. Cardboard flags and weight sets are also all over the place. This is typical. Do not allow this to happen again. W hen you finish a lab you ask if it should be put away and do what you are told.

Rotational KE Lab

Here is the link:

http://h1.ripway.com/DrCherdack/Rotating%20and%20trans%20KE%20lab.doc

Honors Schedule

Here is your assignment for tonight. I would have had a full blown schedule for you but the Rotational Motion Group from Honors 2 took up all my time so here is tonight's assignment for now.

Work on Harmonic Motion Lab
Fix whatever you did wrong on Rev sheet prob 4 and 5 and spread sheet on Harmonic Motion.

AP Sect 5

When you left the room today there were two text books laying on the floor along with two markers and a white board. This is an indication of poor manners and lack of consideration. Please do not let this sort of thing happen again. I would like to continue thinking I am fortunate enough to have fine young people as students.

AP Fluids Schedule

Here is your schedule for fluids. Note that the same physics principles continue to apply to fluids. Work still is the transfer of energy, momentum is still conserved or changed by F from external sources x Dt, and Win = D PE + D KE + losses. In some very real sense all that has changed is that we are dealing with a volume of material instead of individual objects. Fg is still -Mg on earth. Do not be intimated by the new vocabulary we will use to discuss the physics of collections of particles instead of single objects.

Make sure you read and understand the lab (see link below) before we actually do it.

http://h1.ripway.com/DrCherdack/APUnit7Fluidsched-10-11.doc


http://h1.ripway.com/DrCherdack/Notes%20on%20FluidDynamic%203-10.doc


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


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

Honors Corrections

Sorry, there were a couple of typos in recent posts.

KE is Mv^2/2 as you all know and

a = -omega^2 x

Use these corrected equations in the spread sheet and work sheet assignments due yesterday and today.

Tee Shirts, Food Drive

Just do it.

Honors

Honors 3 will not have the computers tomorrow and Friday. Sorry, you'll have to listen to me. We'll do the simple Harmonic Lab. You should have a copy of the 09 version. I posted the '10 version earlier this week. Look it over.


All groups try you best to complete last night's assignment as well as tonight's. Remember that omega =sqrt of (k/M) v =-omega A sin(omega t) and a = -omega^2 x. PE = kx^2/2 create a column next to KE and see if KE + PE is constant.

Tee Shirts

Think how confident you'll feel starting the new year wearing your Ridge Physics T shirt. Orders are due Thursday.

Honors Assignment

Make sure you did the examples posted over the weekend and then try this worksheet. Section2 should be able to do this. Section 3 here is the information you need:

Theta = omega t use this in all the circular equations for x position, vx, and ax, and they are now the right equations for an oscillator, provided omega = sqrt(k/m) and the radius = A = xmax ( maximum displacement from the equilibrium point x=0).



http://h1.ripway.com/DrCherdack/oscprobA4-09.xls

To find the KE just use mass times v^2/2 and for PE use kx^2/2

AP Power in Rotation

Problem 3 in the Rotational Energy WS asked you to find power using torque x omega at 15 and 30 seconds. Try finding the power from the rate of change of rotational KE , i.e. the rate of change of I omega^/2.

To do this remember I is constant so we have I/2 (omegaf^2- omegai^2)/delta t. Approximate omegaf as omegai + alpha delta t. Carry out the (omegai + alpha delta t)^2. Then cancel terms where appropriate and divide the numerator through by delta t . Then let delta t get infinitesimally small so any term with a delta t goes to zero. Use omega at 15 and see if the power matches the one found from torque x omega.

Food Drive

If every student brought in 1 full bag of groceries it would represent a small expenditure per student but a magnificent food drive. Right now 506 has totaled about 12 bags . Figuring all of honors 2 plus all those who are not doing anything in their first period classes we should end up at near 40 bags. Let's get a move on. Place a bag of groceries next to your book bag tonight. Mark a big 506 on it.

All Students - Homework

Put the DUE DATE as given in the schedule and/or blog as well as your name on each assignment. Otherwise you will not get the credit your wonderful efforts deserve.

Simple Harmonic Motion Lab

Here is the link to the updated version. Look it over and see if there are any differences. I know about the fact that it specifies 500g for Parts 3 and 4.

http://h1.ripway.com/DrCherdack/Simple%20Harmonic%20Motion%20Lab-10.doc

AP Assignment

Finish Energy and efficiency you started in class and then do this


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

Honors Schedule

Better late than ...oh. never mind

http://h1.ripway.com/DrCherdack/HonorsUnit6Rot2sch10-11.doc

These are tough but do 4 and 5 on Wednesday [and Thursday only if we don't get to energy on Wednesday.]
http://h1.ripway.com/DrCherdack/RevProbRotandHarmR2.doc

All

1) Tee shirts: bring cash or check but bring money and order sheet. Buy several you can where one each day of the week

2) Food Drive - need I say more. Well I will any way. We are not among the top two classrooms yet. Let's fix that!!

Honors new stuff

1) Make sure you read the previous post and do the reading and assignment

2) Be prepared to do research Thursday and Friday, Look at the list of items I supplied and make sure you can discuss them intelligently by a week from this Thursday.

3) We are moving into oscillations starting Tuesday. We will begin with a comparison of something bouncing back and forth on a spring and something going in a circle. Make sure you read the following by Monday night.

http://h1.ripway.com/DrCherdack/NotesonCircHarmonic2-09.doc

Here are some questions to answer by Wednesday

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

We will also look at conservation of energy in an oscillator. Thus make sure you are familiar with KE and the PE of a spring with a mass attached( k DeltaL^2/2)

4) Here is the lab we will do this week. Read it over by lab day.

http://h1.ripway.com/DrCherdack/Simple%20Harmonic%20Motion%20Lab-09.doc

Honors On Rotational Motion

Here are up to date notes on torque and angular momentum.

http://h1.ripway.com/DrCherdack/NotesonTorquerev12-5-10.doc

They cover some of what the Rotational Motion Group will present tomorrow in period 2 and I will present in period 7. Read them so you will be able to follow it.

For tomorrow answer the following questions based on all you have ( or should have) learned about rotational motion so far.

A solid disk of radius R =50 cm and mass 10 kg is at rest. A tangential force of 10 N is applied at 25 cm from the center of this disk. Note that for a solid disk I = MR^2/2. Also note that 50 cm does not equal 50 m. Find the following:

aplha ( rotational acceleration)

atangential of a point at the edge of the disk i.e. r =50 cm.

After 20 seconds what is:

omega

vtan at the edge

the KE of the disk

the L of the disk

the work done by the torque

the distance traveled by a point on the edge.

the acentripetal of a point on the edge.

Four Words

Food Drive

Tee Shirts

AP Power and Eficiency

You should finish the Power and Efficiency worksheet tonight.

Here it is for those who lost it.
Power and Efficiency Worksheet

Power equals the rate at which work is done or the rate at which energy is transferred from one system or object to another. it is measured in Watts (W)

Power = Work/Dt.

Power x Dt = energy

Power provides an indication of how rapidly work can be done. If you must raise a large mass quickly, you need a more powerful motor to raise it then you would need if you needed to raise it slowly.

Efficiency is the ratio of useful work obtained to the work or energy put in to the effort. This is also described as work out /work in

eff = Woutput/Winput one symbol used for efficiency is , the Greek letter eta.

Examples: a) What is the power required to lift a 1kg mass 15 m in 5 sec?


b) The motor receives 45 W from the power company. What is the efficiency of the motor and the lifting machine? Since the useful power obtained is 30 W and the input power is 45 W, the efficiency is 30/45 = 0.67 or 67%.

1) What power is required to lift 20 kg 25 m in 30 sec?

2) How much power is required to change the kinetic energy of a car by 1,200,00J in 3 seconds? (ignore friction, etc.)

3) How much power is required to accelerate a 1400 kg car from 15 m/s to
20 m/s in 3 seconds?

4) If the engine actually delivers a power of 120,000 W during this time and the increase in kinetic energy is considered the only useful work, what is the efficiency of the process?

5) A light bulb receives 60 W of power for 20 minutes. How many J of energy did it receive?

AP Collision derivation

Read this for tomorrow

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

Honors assignment

Do the following use torque = alpha I and the kinematic equations supplied earlier

A torque of 40 Nm is applied to a wheel at rest with an I of 3. What is alpha? What is omega after 3 seconds, 20 seconds;what is delta theta after 3 seconds, 20 seconds?

Using I omega squared/2 = KE rotational, what is the KE after 3 seconds and 20 seconds?

If torque equals work per radian traveled what is the work done in 3 seconds, 20 seconds? (Please, please, please know that delta theta is radians traveled in this application). Does this match the change in KE?

Honors Research Topoics

1) TV group I have not forgotten you. Since your topic is a combination of electric force, magnetic force and electrons interacting with atoms to produce light, you should look over those topics in the light and magnetic groups. You also should understand how highly energetic electrons interact with phosphors to produce light. Each electron must produce thousands of photons.

2) laser group is also not forgotten. Understand light and then investigate energy levels of interest in lasing. How are electrons excited to these levels without causing them to emit before they are pulsed. Find out how the lasers in pointers and CD players work. What are substances used, how are they energized (pumped), light frequencies, how frequently they are pulsed, how are pulses focused or aimed.

Food Drive

Guys, you've been great so far but let's make a big push for the end. Now that we are all overfed from this past weekend, let's be generous to others. Pick up several items on sale and bring them in. Place them by your book bag the night before.

Honors Section2 Fire Drill Thursday

Fire drill Thursday at 9:03. Bring coats if its cold.

Honors Sub topics for research

Here are the topics I think you should cover in your research. Some groups have a long list so I don't insist everything in your list to be covered by those groups, but give it your best shot.

Most important: You must understand what you present.

You will present a series of lessons using white board and or slide shows. Labs and demos are even better.

You will also supply a written report to me containing everything you present and a bibliography of references.


Research subtopics for Honors

A. Magnetics
1. Why currents produce magnetic fields that affect a moving charge
a) Force between charges – Coulomb’s law, electric field
b) electric field
c) define a current
d) Lorentz contraction of moving charge
e) F =qvXB defines B
f) B forms loop around current
2. Force on currents
a) get from qvXB to F= ILXB use I = (q/L) v
3. Why moving field produces force on static charge
a) B lines are closed loops
b) v is relative velocity of q to B
c) B moving through closed loop

B. Light
1. What is light
a. Classical electromagnetic wave explanation of transverse wave
b. Frequency and wavelength range
2. Light and atoms
a) Bohr model – electric force = centripetal force, KE vs PE allowable energies and radii for Hydrogen
3. Optics
a) refraction: Snel’s law, total internal reflection
b) Lenses and images

C. Sound Waves
1. Compressive waves
a) general model wavelength =c T
b) solid or spring
c) pressure relationship to number of particles/mcubed in gas
2. Speed of compression wave
a) solid
b) liquid
c) gas – how temperature affects it need to know some thermodynamics
3. Wave energy and momentum
a) calculate as function of amplitude, speed , and materials
b) reflection and transmission at interfaces

D. Cosmology/Black Holes
1. Gravitation
a) Equation for F of grav. Circular orbit FG = Mac
b) Potential energy and KE for circular orbit
2. Light and gravity
a) Mass of photon from Energy = hf and E= mc^2
b) Schwartzchild radius ( event horizon)
3. Black Hole formation
a) processes for star
b) Mass needed
4. Time dilation at/in black hole
a) Relativity effects of gravity

E. Music
1. Define resonance
a) wave pattern wavelength = cT
b) wave speed on string – speed of sound see above
c) types of reflection – fixed and free end
2. Standing waves on string frequencies and wave lengths
a) from node location; fundamental and harmonics
b) from speed and reflection; fundamental and harmonics
3. Standing waves in air column frequencies and wave lengths
a) from node location; fundamental and harmonics
b) from speed and reflection; fundamental and harmonics
c) reed resonance

F. Particle Physics
1. Types
a) leptons and quarks
b) hadrons
c) “force particles”
2. Four forces
a) particle quantities ( charge weak charge color)
b) interaction results
3. Rules for particle creation
a) energy conservation
b) charge conservation
c) baryon number
d) generations
4. Accelerators
a) types
b) principles of operation
c) key specs for a few accelerators
5. Detectors
a) principles of operation
b) properties for each particle type
6. Why colliders?

G. Ocean Waves
1. Describe wave
a) particle motion
b) shape
c) wavelength
d) speed
2. Formation
a) By wind
c) Tsunami
3. Behavior at shore
a) interaction with bottom
b) change in depth
c) change in speed and height ( conservation of energy and momentum)
d) collapse and curl
e) undertow

Retests

There will be retests available Thursday for

Honors who got a score ( not a %) of 80 or less on the last test. Highest grade on retest will be 80

AP Section 4 who scored less than 90

AP Section 5 who scored less than 80.

Highest grades on retest will be a B-

Monday and Tuesday

I will be out Monday and probably Tuesday. Apologies to those with appointments. Please be good for the sub. Worksheets will be handed out, I hope, please try them individually and then by group.

Honors Lab

Both sections read this. It will help Section 2 write reports and Section 3 understand what they'll be doing Thursday

All the PE initial should ( i.e. is expected to) become KE at the bottom. KE has both rotational and translational (linear) parts. Rotational KE is I omega ^2/2 and

I for a sphere is 2MR^2/5 so we have

KE rotational = 2MR^2/5 times omega ^2 /2 or
KE rotational = 2M(R omega)^2/5 /2 and of course R omega = v so

rotational KE is 2Mv^2/5 /2 = Mv^2/5.

Translational KE is Mv^2/2 so

total KE is (1/5 +1/2) Mv^2 = .7 Mv^2.

From this you should be able to find your expected value for v given your initial PE (i.e. Mgh).

This is already too much help. You should be able to r the rest now. Remember, discussion should be more than answering lab sheet questions. You must decide if our hypothesis about total KE is correct.Thus, you must find percent error using either measured vs expected v or measured vs expected KE.

Honors Assignment

In order to learn about waves we need to learn a bit more about rotational motion and then about oscillations. Here are some notes and problems about linear and rotational motion. Read the notes and do the problems for Monday. Also try writing the equations for tangential motion. They should come out as corresponding to the linear motions equations except with tan subscript for v and a and an s instead of x

HTML Link:http://h1.ripway.com/DrCherdack/Linear%20and%20Rotational%20Kinr1.doc

If you want get a heads up on where you will be going with waves read the first few parts of these notes. Go as far as you can if you are in a wave related group.

http://h1.ripway.com/DrCherdack/Notes%20on%20Waves11-10.doc

Also read these about wave speeds if you are in a wave group
Speed of Longitudinal Wave
http://h1.ripway.com/DrCherdack/MaterialPropertiesandLongr1.doc

Speed of Transverse Wave

http://h1.ripway.com/DrCherdack/NotesonTransverseWaveSpeedR1.doc

Honors Research work

I see I did not make my wishes clear last time. Please identify 3 major facts, equations, relationships, that are fundamental to your topic and that you will teach the class. Place these (one per group) in the in folder making sure they are marked as project work somewhere in the title and also dated.

AP Lab for Wednesday

Please read this so we can do this lab quickly tomorrow.

Power Lab

In this lab we will determine the power you deliver in raising yourself with and without the average back pack one story. You will calculate the change in potential energy you gain and the time it takes you to gain it. Finding the ratio will give you the power you deliver running up the stairs.

Facts you may need:

1 horsepower = 746watts

1lb mass = .454 kg

g =9.8 N/kg

P=W/Dt

W= DKE +DPE. Find KE using v found from distance = (Dh/cos (45)) +2

Procedure:

Choose a timer, a runner, and a starter for your group. Starter stays at the bottom and timer stands at the top. . Make sure your timer can here you when the runner starts.

Measure the change in height from the first to the second floor.

Measure the runner’s weight in lbs and the backpack’s

Runner ______lb Pack _____ lb convert these to kg for use in finding Joules and Watts

The runner will make 4 runs:

one at a walk without the pack;

one at a walk with the pack;

one at top speed with the pack

one at top speed without

Calculate the power for each run in watts ( 1 watt = 1 J/s). Analyze the effects of change in speed and work done on the power.

Is the kinetic energy is negligible compared to the gain in potential energy?

Everyone

Last chance to bring in food before Thanksgiving.

Honors Assignment

Section 2:

1) Recalling that torque is work per radian, find how much work is done by a force of 300 N applied to a sprocket of radius 6 cm (not m)on a bicycle wheel when the wheel makes 3 turns. Assume the wheel is attached to a bicycle with a rider on it with a total mass of 100 kg, and the the bike was at rest to begin with. How fast is the bike going after three turns of the wheel ( note sprocket and wheel turn together - the sprocket is the gear on a bike's rear wheel)? Use the relationship between work done and KE to figure this out.

2) If all the wheel's mass of 1 kg is at the rim how much rotational KE does the wheel have at the speed you just found? Is it important compared to the total KE so that you need to revise your calculation or is it negligible?

Show all work.

Section 3: Recall that angular acceleration, alpha, is torque/I. If a force (all tangential) of twenty Newtons is applied to the end of a .4 m long crank attached to a disk with a moment of inertia (I) of .5 kg m^2, what is the resulting alpha? What is omega after two seconds? Repeat the problem only with a force of 80 N.

Honors Assignment

For Monday, read Torque Notes and do this sheet.


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

Nice Work

Nice work on the food drive; but we have along way to go. If you haven't brought any, bring food Monday. If you have, keep up the good work. Shop for rice and cereal or good canned goods on sale this weekend and place them near your book bag Sunday night.

Have a good weekend.

TWO MORE WORDS

MORE FOOD

Honors

We will be doing research over the next few days combined with learning more about torque and energy of rotational motion. For tomorrow, be prepared for doing research on the web or in books. Group should present three concepts, relationships, equations concerning their topic by the end of the period, so get started tonight.
Read Notes on Torque over the weekend. [ If you get those dopey little boxes just highlight them, change the font to symbol and translate from the Greek - its really not hard to figure out what the letters should be.]


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

AP Energy and Work Unit 6 Schedule

Here it is
HTML Link:
http://h1.ripway.com/DrCherdack/AP%20unit%206%20Energysched-10-11.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

TWO WORDS

Food Drive (set the food out tonight so you won't forget it tomorrow)

DeltaKE vs-delta PE lab

Here is the lab sheet


http://h1.ripway.com/DrCherdack/Lab%20on%20Del%20KE%20=%20-Del%20PE_11-10.doc

Group reports

Reminder AP group reports once a week or no grade. Honors, once a unit or no grade.

AP Book Problem Answer

Chapter 9 problem 17 answer is 1.43 NOT .143 m/s

University of Richmond Physics

For those of you thinking about where to apply for college, here is a note I received from a professor at University of Richmond [The links are not live so contact me if you want more information]:

Last fall I wrote to you as one physics teacher to another to tell you about several opportunities in physics at the University of Richmond. I’m writing to you again to share with you some of the highlights from the previous year, in the hopes that you will pass this information on to any of your students who may be interested in pursuing physics and finding out more about our department.

• Last year, in addition to our regular courses, offered additional elective courses in optics, electronics, and advanced quantum mechanics. Our advanced courses typically have about 12 students in each class. (Even our first-year physics courses are capped at 24 students each. None of our physics courses are taught by TAs or graduate students.)
  

• Our six tenure track professors published 34 physics articles in major research journals last year, demonstrating that our faculty are respected leaders in their fields. Moreover, nine students were coauthors on these papers, demonstrating real undergraduate involvement in cutting edge research.

• Professor Ted Bunn won a $187,000 grant from the National Science Foundation to study cosmic microwave background radiation. He and Professor Jerry Gilfoyle were also awarded $162,000 from the NSF for a new supercomputer cluster. Professor Con Beausang won three new awards from the Department of Energy ($143,000 total) for studying nuclear physics. From these and other ongoing grants, we paid salaries for 17 undergraduate students doing summer physics research in 2010.

• Ten students traveled to national and international physics conferences this year (including meetings in Hawaii, San Francisco, and Washington, D.C.) to present results of their research with their professors.

The University of Richmond is a highly selective liberal arts university with just over 3,000 students, offering small classes and opportunities for one-on-one work with professors. Our small size and tremendous resources give our students many opportunities to do real cutting-edge research as undergraduates.

It would be my pleasure to talk with you or your students personally about our program; you can contact me directly either by email or by phone. I hope that I will have the opportunity to speak with you and your students sometime soon!

Food Drive

Ridge is having its food drive again. Honors 2 should bring food to 506. Any other students not participating in a first period food drive in some other room should bring food to 506.

THIS DOES NOT MEAN BRING IN A PIZZA FOR YOU.

It means bring in nonperishable food for those less fortunate. Bring it in and bring it often.

Here is part of the announcement: [and by the way, if we can wait two weeks for a pickup I will be terribly dis appointed in you folks.]

The pantry will accept any non-perishable items, but there is a significant need for coffee, cereal, rice, and sugar. Donations will be collected by the sophomore class officers every two weeks (unless you need an early pick-up, in which case you can email us). As a token of our appreciation (and a little bit of bribery), the class with the highest number of donations (throughout the month-long challenge) will be rewarded with a DELICIOUS BAGEL PARTY! Please encourage your class to donate!

Grades on HAC

I have posted your quarter grades on the High Anxiety Center. They appear as "Project 11/9 Qrtr Grade" or whatever HAC translates my entry into. This is the grade that should appear on your "report card". On the whole they are pretty high and nice work folks.

If you are feeling any sense of gratitude about your grade, I wouldn't mind seeing a little red two seater in my parking spot when I come to work some morning, preferably something with a prancing stallion as its emblem.

In the mean time, particularly honors, while most of you can be pretty satisfied with your performance to date, the bar is being raised, so do not relax. In fact, try even harder.

Honors Rotational Motion Schedule

Here is your new schedule. Once again, theta looks like an O and omega looks like a w. This is really not my fault. Despite what many of you may think, I was not around when the Greek and Roman alphabets were developed.

Note the test or quiz on Thursday.

http://h1.ripway.com/DrCherdack/HonorsUnit5Rotsch10-11.doc

AP Data

Here it is for both sections. Enjoy what looks to be a really nice weekend. Formal Lab report due Tuesday.


http://h1.ripway.com/DrCherdack/AP4%20Pmomentum%20Reading.xls


http://h1.ripway.com/DrCherdack/AP5%20Momentum%20Data.xls

AP Section 5 Data

See if you can complete the columns to calculate pA pB pA' pB' and find the if the momentum before = momentum after and % error and also if delta pA = - delta pB and % error. We'll do some more runs tomorrow.

http://h1.ripway.com/DrCherdack/AP5%20Momentum%20Data.xls

Honors Centripetal Problems

Do these as well as the second problem sheet tonight.


Centripetal Acceleration and Force Problems.

1. A 1800 kg car going at 55 mph ( 1 m/s =2.24 mph) goes around a curve with a radius of 100m. What is the car’s centripetal acceleration, ac? What is the friction force required for it to make this turn?

2. A satellite of 80 kg mass orbits the earth at a distance of 6.6x10^6 m from the earth’s center. It makes one orbit (one rotation) in 5300 seconds. What is its ac? What is the force required to keep it in orbit? What supplies this force (what kind of force is it)?

Summer program

Here is info about a science, engineering , pre med program for juniors at Vanderbilt. If you are interested in doing this let me know by email immediately. You do not have to commit to it now, just say you might want to do it. [This is not a live link. You'll have to enter this URL manually.]

https://pave.vanderbilt.edu/ayindex.php

Honors Rotational Motion

Here are some materials. Read the definitions etc. Do the simple problems tonight. The other sheet tomorrow night.


http://h1.ripway.com/DrCherdack/Rotational%20Motion%20Defns%20etc.doc


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

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

AP Schedule Unit 5

Here it is


http://h1.ripway.com/DrCherdack/APUnit5MomntumSched10-11.doc

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


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


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

AP Orbit Equations

Note that ac = Fc/Msat so that v^2/r = G Mcentral/r^2 thus v^2 is proportional to 1/r

AP Assignment

Read Chapt 9 and Sect 1,2,3 make sure you read pg 265 and think Fnet avg where book uses Favg

Do Chapt 9 Quest 1 , 2 ( use concepts of not just equations of Fnet =Ma and Delta v =a Delta t in your explanation) MC 19 problems 1,3,7

Calculators in 506

Someone removed a TI 83 from 506 today. It has initials CI on the back; please return it.
Two more modern TIs were left in 506 . Contact me if you are missing one.

Honors Lab on Power

Lab sheet has a n error 1 kg = 2.205 LB NOT the other way around.

Lab report is informal. Please share data with the cross country runners and other absentees

HAC

Every time I post grades on HAC I get a bunch of emails from people who do not bother reading the notice. The post announcing the grades said "Just your test/quiz, lab and homework grades are relevant." Your project grades are not posted because your project inputs have come in in ways that require lots of sorting out, like printing emails that do not describe whether they are for groups or individuals, topics or questions, etc.

AP Sheet R2

Please use this instead of old R-2 if you are doing R-2 problems. It fixes some sloppines on question 2.

http://h1.ripway.com/DrCherdack/Problem%20Sheet%20R-2clean.doc

Grades on HAC

Your grades are now posted on the Home Accident Center. Pay no attention to the overall grade. Just your test/quiz, lab and homework grades are relevant. Many of you have very low grades on labs because you had not submitted or resubmitted labs. See me s becomes a 60 or less unless rectified. We seem to be having a crisis in Honors Section 3 with labs just not coming in. The labs are 20 % of the course, act accordingly.

I'll try to post Honors project grades soon. For many of your questions it was not clear whether they were group or individual questions. Please make sure you have both in.

Honors Waves

All of you doing light and sound and ocean waves should read the notes on waves (all); material properties and longitudinal waves (sound) and transverse waves ( light and resonance for string instruments). Notes on optics are helpful for those working on those lenses and reflections. Resonance is associated with what are called standing waves so those doing instruments should try the worksheet on standing waves

http://h1.ripway.com/DrCherdack/Notes%20on%20Waves4-10.doc


http://h1.ripway.com/DrCherdack/MaterialPropertiesandLongr1.doc


http://h1.ripway.com/DrCherdack/NotesonTransverseWaveSpeedR1.doc

http://h1.ripway.com/DrCherdack/NotesonGeometricOptics4-10.doc

http://h1.ripway.com/DrCherdack/StandingWavesworksheet22-08.doc

All Students

Have a happy Halloween, and a safe one. After all I don't want you spilling your blood where it will be wasted.

AP Advanced Assignment.

The Torque lab advanced assignment is due on this Monday.

Honors Presentations

You have two project related assignments for this weekend

1) Each group should come up with two questions with which I can help them . They should be specific in nature so that I can walk you through what you need to know in 15 minutes or less. This is to make me feel useful. These are to be emailed to me over the weekend.

2) Each group has to provide me with hard copy of what they are presenting so I will have more than a vague recollection to go on after the class ends.

Honors Momentum Lab Reports

You lab reports must include a printout of the spreadsheets showing your results to be complete. I am not about to printout the spreadsheets from your emails, nor have I memorized your results.

Prepare the spreadsheet for printout as I showed you in class

with gridlines
covering two pages
in landscape
with the first 3 columns ( run number, Mass W, Mass D) repeated on the second page.

Honors projects

This what my records currently show. I certainly may have missed some emails with topics and URLs so come see me if you have some items not showing. If you have not submitted some items, Monday is the deadline. Presentation grades are for the entire group.

http://h1.ripway.com/DrCherdack/Projects10-27.xls

Honors Homework

Here is what I show at the moment


http://h1.ripway.com/DrCherdack/Honors%20Homework10-27.xls

Honors Retest

There will be a retest available to those who got below 35 as their score ( score not grade) on the last quiz. The usual rules apply. Your maximum grade on the retest will be the equivalent of a score of 35 i.e. a weak B-. You must email me by Friday 7:25 AM if you wish to take it. Your homework must be up to date e.g a homework grade of over 90.

AP Section 5 Pulley Labs

Section 5: I am missing about 1/2 your pulley labs. They are now 2 days late.

AP Retest

You can raise your grade to a 78 by taking the retest on Thursday. You must email me by Wednesday AM and be up to date with your homework to take the test.

Honors Schedule

Now that we have finished ( I hope) the dread momentum conservation lab here is the schedule for energy and work. Go back and make sure you have the Notes on Work and Energy and Notes on Energy Fundamentals from previous posts. If you do the reading this unit will be pretty straight forward and if you don't.... well just do the reading.

http://h1.ripway.com/DrCherdack/HonrUnit4EnrgyandWrk%2010-11.doc

http://h1.ripway.com/DrCherdack/EnergyandWorkWorksheet1a.doc

http://h1.ripway.com/DrCherdack/Hnrenrgy%20andlossProbs%20.doc

Honors Spreadsheets

So far I have received spreadsheets from fewer than half of you. I offered you an opportunity to get a bit more credit for doing something you had to do anyway. Now it looks like many of you will get zeroes for something worth half a lab.

I will bear this sad experience in mind in the future.

AP Material

here are the links: Read the "planets or satellites in orbit" notes tonight.

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/ProblemSheetR-1rev1.doc

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


http://h1.ripway.com/DrCherdack/ProblemSheetR-3.doc


http://h1.ripway.com/DrCherdack/Planets%20WS.xls

Honors lab

You don't need to graph anything. Do a good formal lab. The purpose is pretty obvious. Your discussion should cover how we calculated the various values and how close did we come to demonstrating what we set out to. The conclusion should refer back to the purpose and spell out if we made a case for what we tried to prove. Were our errors still small enough to make our case plausible?

Honors momentum labs

I don't know how much more explicit I can make this .The excel file you send me has to have your name in the file name. If it did not, send the file with a its new name again and tell me its a resend in the message subject line.
I don't need 42 spreadsheet files with the same name.

Honors Projects and Section 3 ( period 7)Homework

By now each group should have turned in its logo and name.
Each student should have turned the following 3 assignments 1) actual topics you will cover, 2) two key questions about your topic you think you answer in doing your project 3) websites you have used and a very brief summary of what you learned on the website and relevant text sections [Waves people should see fluids and waves chapters in text. They provide some important background to tides and riptides; but do not get wrapped up in wavelengths and sine waves].

Thus each group should have turned in an assignment and each student should have turned in 3 individual assignments.

Section 3

I looked over your project work and it ranged from very good to excellent. However it was also very incomplete. Homeworks turned in range from 13 to 26 assignments. You should ahve at the very least 24turned in.

Section 2 ( period 2) You folks are more complete but nearly no two questions assignment have been turned in yet. Please turn in assignments now if you haven't yet done so.


I will try to post my records on projects and home work by Tuesday so you can see what is missing. If you can't stand to have others see your project or home work records email me ASAP. Who knows I might even get the message before Thnksgiving.

Email

Its down again as of 11 AM Sunday. I'll check later to see if its up.

Honors Momentum Data

Here are spread sheets with all the values. Read the notes since I have edited the data in one run for each class to correct what I think were errors in reading or recording times.

Make sure you use your section's data.

Note there are no equations on these sheets. Your job is to replace the values with the correct equations in each line. To do this save the sheet with values first than save it as a file with the file name: yourname_momentumH2 or H3 depending on your section. Please use your own name not "yourname"!!!! Then email the file to me. This file will be considered a separate lab worth 1/2 a lab by itself.

The equations for the pD, pD', pW and pW' and for p'-p and delta pW + Delta pD, and %error are the same for all cases.

The equations for the velocities are the only ones that change from case to case. For the first runs with vW =0 if cart D is more massive than cart W ( or even equal) then TW2 gives cart Ds post crash velocity, vD' , because D kept going forward. If cart D is lighter than TD2 gives vD' and it should be negative, because D bounced backwards.

When vW (initial W velocity) not equal zero the vW is negative and is given by TW1, vW' is given by TW2 and is +, and vD' is given by TD2 and is negative.

If I get a chance I 'll post the equations after you turn your labs in.

http://h1.ripway.com/DrCherdack/MomentumvaluesHon3%2010-22.xls

http://h1.ripway.com/DrCherdack/Momentum%20valuesHon%202%2010-22.xls

AP Schedule

Correct link is now posted, but here it is again,

http://h1.ripway.com/DrCherdack/APUnit4schedrotmot10-11.doc

AP Unit 4 Schedule

Here's the schedule. Worksheets etc. to follow. Read the notes posted yesterday.


http://h1.ripway.com/DrCherdack/APUnit4schedrotmot10-11.doc

Honors Section 2 Data

http://h1.ripway.com/DrCherdack/Copy%20of%20Momentum%20Data%20Sheet%20Honors2a.xls

Honors lab data

I am giving you links to data sheets with the equations but you must make sure you understand where the equations come from and why they are right. Note that the velocity equations can change if conditions such as cart masses and which cart(s) is moving initially and direction matters. Jack and I did some of the Section 3 runs rerun of 6 and a new run 9 - in 9 we had car d stand still and car w moving at first. We may do few more trials tomorrow.

http://h1.ripway.com/DrCherdack/Momentum%20Data%20Sheet%20Honors2.xls


http://h1.ripway.com/DrCherdack/Momentumlabsect3.xls

AP Assignment

Here's tonight's assignment, stay tuned for Unit Schedule.

Read Definitions for Rotational Motion pages 1 and 2 and Chapt 6 Sect 1 and 2 . Do conceptual questions 1,3, and problems 1 and 7.


http://h1.ripway.com/DrCherdack/RotMotionDefseetc-07.doc

Honors Assignment Projects

Section 2 Those who did not present last week will present on Monday.

Section 3 each group must make a six minute presentation on their topics on Monday

HONORS 3 DATA SHEET

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

Honors Assignment

For section 2 do the energy assignments that section3 did the other day see earlier posts.

For everyone:

1) Read these notes, they will help you a great deal. Do not worry about losses for now or about forces not in same direction as distance traveled.

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

2) Do the following problems [You can use the following equation

change in position = (vfinal squared - v initial squared)/(2 x acceleration)

to find the final velocity if you rewrite it for vfinal =.....(you figure it out)....


for falling objects and any other time you do not know vfinal]
(use g =10 for the acceleration of an object in free fall on earth )

1) A 4 kg flower pot falls off a shelf 3 m above the ground. How fast is it going just before it hits the ground? What is its KE. Compare it with Mass x g x change in height. Is this the work done by gravity on the pot? Is it equal to the loss in PE?

2) A 1500 kg car accelerates from zero to 20 m/s in 4 seconds. About how far did it travel ?( Figure out v average from vinitial and v final and use it to find how far the car went in 4 seconds.) What was the net force on it to cause this acceleration. Given Fnet and distance, how much work was done? What was the final KE? Are the work done and KE equal.

3) If you lift a 20 kg crate 12 m how much work did you do? How much PE did the crate gain? How fast will it be going if it falls back the 12 m? How much KE will it have gained falling the 12 m? Does this match the PE lost?

Cosmic Rays This Saturday

If anyone would like to learn about cosmic ray detectors and how to use them this Saturday and maybe become eligible for a summer program of paid study at Rutgers let me know ASAP.

Outside Physics and Science Opportunities

Those of you with a real interest in physics or other sciences should investigate opportunities to s participate in outside programs. Here is a list of examples I assembled over the past few years.

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

Columbia Master Class

Here is something people thinking about attending Columbia might enjoy.

http://www.studentaffairs.columbia.edu/admissions/events/sciencemasterclass.php

Honors assignment

What is the KE of a 1500 kg car going 30 m/s .

Was this the amount of work done on the car to make it reach this speed ( ignore drag and friction)?

If the car took 150 m to reach this speed, how great was the net force on car?

How much work does it take to lift a 20 kg book bag 4 m? Why do you have such a heavy bag?

AP Text problem 57

As far as I can figure it out the block will accelerate downward unless there is friction. Try figuring out the the required coeff of friction for it to remain motionless.

Honors Data Sheet

The link in the previous post now works

Honors Assignment

Section 2: use the data sheet to find vdoor, vwindow,vdoor',vwindow' and then for the first four runs find the momenta of the carts. See if total momentum is conserved. Remember to use signs for direction. Make sure you know which car went through which gate when.http://h1.ripway.com/DrCherdack/Momentum%20Data%20Sheet%20Honors2.xls

Section 3: answer the following: A 10 kg mass is lifted 5 m and placed on a ledge. How much work was done to lift it? What was the change in its Potential Energy (PE)? If it falls the the 5 m how fast will it be going, ( remember equations relating velocity, acceleration, and displacement - look over your a=f/m lab if you need help)? How much PE did it lose?

What will its kinetic energy (KE) be?


How much work is done by pushing a 50 kg mass with a force of 20N for 10 m. Assuming there no other horizontal forces, how much KE will it gain? How fast will it be going?

Missing Lab

If anyone picked up Alex Huynh's a=F/M lab please place it in the yellow out folder and let me know

Group Reports Urgent

I received a single study group report for an entire group. This is NOT acceptable and must be replaced by reports from each member

Honors Assignment

Read Chapter 6 the first 4 sections and read notes on energy fundamentals.

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

Answer the following:

Force F acting for a time delta t changes p by delta p = F delta t. Write a similar relationship for force, delta x and energy.

When you lift an object without changing its speed what changes?

What is the change in potential energy when you lift a 1 kg mass 3 m?

I f you apply a force of 10 N for 3 m to an object what is the change in the object's energy?

Honors Momentum Problem Sheet

The correct answer for the the force vs time graph problem is a graph that is three times as wide and one third as high. For example it could be a triangle whose base runs from .05 sec to 0.5 sec and it should reach a maximum of about 8400 Newtons. The area under must be the same as the original since delta p is the saem because M(vf-vi) does not change.

Group Reports

See earlier post of Sunday 10/10: study group reports from AP are due on Mondays, from honors on day of quiz. These are required! BRING THEM IN

Honors problem Sheet

For problem 11 just find the velocity after the collision. The height requires that you know something about energy, and we have discussed this yet.

Honors

The honors test will now be a quiz given on Friday . This will allow full 2 periods for our computer lab for Honors Sect 3. Honors Section 3 make sure you bring all your a=F/M labs in with your data.

AP Test

The AP test is now a quiz and will be on Friday

AP Quiz

The quiz on forces will be on Thursday. Problems and questions will focus on important ideas not super manipulations of equations.

Honors Homework

Your schedule should call for problem 10 instead of 9 on the extra problem sheet. Problem 10 is tough so don't kill yourself over it but give it some thought. We'll try to get to it tomorrow.

AP and HONORS Group Reports

Written group meeting reports are required for every unit from honors. Due on test day for the unit

Weekly reports are required for AP classes. Due Mondays.

Meetings are to take place outside of class hours and should be at least 40 minutes long. Attendance is to be in person unless absolutely impossible for someone to physically attend.

Reports are required from each student and contain the following:

Place

Date

Persons present

Topic discussed (real topic including Unit name and number, not just problems, or homework)

All Students (and the rest of you in my classes)

I learned from back to school night that a few of you are spending too much time on physics at home. Yes you read that correctly, it is possible to spend too much time on physics. Do not spend more than 90 minutes a night on problems unless you have the time and energy to spare and you are enjoying the challenge. If you are stuck, try your group members first. if that doesn't work, you can always email me or ask me the next day.

You should be spending about 7 to 8 hours a week outside class on this subject, probably the toughest course you'll take at Ridge.

In any case coming to school alert is more important than solving every bit of homework.

Honors Projects

1) I should be receiving emails which contain links to sites you plan to use and a paragraph describing your topic in detail and what you learned or hope to learn from this site(s) in your own words

2) Try your best to catch up on your momentum homework without exhausting yourself. Bring an alert mind to school.

3) Particle Physics group: here are some notes for you. Go through the energy notes first, we'll cover this in our next unit after momentum. Nest read the particle physics notes. Don't spend much time on the equations, and relativity but do try to get familiar with the ideas and vocabulary of the particles and forces. An important concept is that energy can be converted into matter, (Mass=Energy/c^2) so fast moving particles can interact to create new particles with more mass than the original particles had.

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

http://h1.ripway.com/DrCherdack/Notes%20On%20Particle%20Physics.doc

AP Retest

The AP Retest will be given tomorrow. I know there are difficulties, but my experience indicates that delays will only reduce your readiness.

Honors Test

Nice Work guys, average was about 84% correct.

AP Projectile Motion Lab

The lab's purpose was not to find out how far the ball would go. Nor was it to improve your already immense prowess in projectile motion. It was to confirm the concepts and equations we use in calculating projectile motion. Even an error of 5 or even 10% is not so terrible when you consider that the predicted distance was the result of several rough horizontal and vertical measurements and 4 sequential calculations.

Honors

Remember tomorrow is a project day. Be prepared

All classes a=F/M lab

For this lab the force was clearly defined and even calculated for you at the top of the data table for run 1. It is the hanging mass x g = .1 kg x 9.8N/kg ( use 9.8 for labs) =.98 N for Run 1. Force for run2 = .05 kg x 9.8 N/kg = .49 N. The slope you find from your graphs is not force, it is Ma. You were supposed to compare your slope with the force ( .98 N or .49 N depending on the run). If you found your acceleration in cm /s^2 and graphed it without dividing by 100 to get m/s^2 then you need to divide your slope by 100 to compare with the force in N since 1 N is 1 kg m/s^2 NOT 1kg cm/s^2.

Some of you found the force as if the hanging mass were 100 kg instead 100 g = .1 kg. This gives a force that is a factor of 1000 high.

Some of you found the slope and called it the force and then divided it by mass and got your acceleration. This does not prove F= Ma. It proves that Ma/M =a, something that is pretty well established .

To repeat the most important point: you must compare your slope in units of kg m/s^2 with the force ( .98N or .49N) that was accelerating the system.

Honors Practice Test

AP a =F/M Lab

The sentence just before question 5 refers to the timer tape results. Ignore this. Its from when the lab was a much longer affair.

Honors Test

Test Results

Grading them took about 6 hours between AP and Honors because I spent a lot of time trying to figure out what you were trying to do. It looks like we'll be doing some serious reviewing in most classes

Honors

One sign of maturity is taking project assignments seriously. They are even more important than worksheet or text book assignments. For those of you still in the grades before learning mode of thinking, note that project assignments count towards both homework and project grades.

Topic names and logos are overdue in many cases. Hard copies by Monday or zeroes will start show up.

Honors Momentum Schedule and Materials

Here is your new Unit 3 Schedule and two sheets

http://h1.ripway.com/DrCherdack/HonUnit3-1DMomSched10-11.doc


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


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

AP Ferryman Lab

There is a fair amount of confusion about this lab so let me try to sort it out here.

We did most of the activities in class. First we had o river current. The boat crossed the river going 100.8 m in 5.04 s indicating that its velocity with respect to the water [ v b,w] was 20 m/s and in this case due north. The with the boat point straight north , i.e. heading = 0 deg, we set the current to 10 m/s. The simulation gave the x displacement as 50.4 m and the y as 100.8. The time again was 5.04 seconds. From this we calculated the total distance traveled and the speed wiht respect to the shore by dividing this distance by the time. We then calculated the velocity using velocity components of vx = 10 m/s and vy = 20 m/s.

We the tried to steer the boat so it would go straight across the river. This required that the component of vb,w in the x direction be -10 m/s . Since we knew vb,w had a magnitude of 20 m/s we could find the direction. Since the simulation reads direction as angle from north ( i.e. theta y) we could find theta x using inv cos (x component/20)and then its complement which would be theta y.

You should be able to include all this in your report and then do the additional work called for. This is all due Monday and is informal.

A purpose and conclusion are required. Did we prove or demonstrate anything ( components, relative velocity, etc.?)

Science and Engineering Fair

Here is a site about a science exhibition and and festival at the end of October.

http://www.njsciencefestival.org

AP Section 5

Several people wrote on the tests despite clear written and oral instructions to not do so. I hate to resort to such silly measures, but next time I will deduct points for tests that have been written on. Checking tests for writing is not a productive use of time and I hope you can show enough maturity in the future to allow us to dispense with this.

AP Unit 3 Schedule

This is the new schedule. It may be revised so stay posted.

http://h1.ripway.com/DrCherdack/APunit3sched%2010-11.doc


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


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


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

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

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

Honors Assignment

Your assignment for this weekend is two -fold

1) We are beginning to study momentum so read the notes and do the problems at the end. The notes give you all the information you need to answer the problems.

http://h1.ripway.com/DrCherdack/Notes%20on%20MomentumRev2.doc

2) Each student must turn in one hard copy paragraph describing in some detail their chosen topic. Do not pass around one file. Also send me your logo and name in one email per group. These are required.

AP Boat Lab

Add a purpose and conclusion. Were we trying to demonstrate something? Did we succeed?

I think I've got it where I want it with respect to the calculations I'd like you to make. The extra lab credit is unusual in that it will be applied to your lab grade directly.

http://h1.ripway.com/DrCherdack/ferryman%209-10.doc

Torque on Honors Test

Since we have covered torque in class and especially in our labs, it is reasonable find out what you learned about it. If you can handle problems of the level of difficulty (not necessarily the same type) of question 6 on your torque lab, you should be okay.

There is a post discussing question 6 in you lab from last Sunday. It might help you.

Forces on Objects and Systems

Notes on Forces

A) Note that any single object, call it object A, is affected only by the forces acting directly on it including only contact forces (such as from ropes or table tops)and field forces( such as gravity. This means that only forces from objects in contact with object A or producing a field such as gravitational or electrostatic, which interacts with it, can directly cause object A to accelerate.

For example, without taking into account air resistance and other minor effects, the acceleration of an object hanging from a cable is affected by only two forces, the tension in the cable and gravity. Similarly, the tension in the cable where it is attached to the object can be found by considering only the acceleration of the object and the other force on the object and keeping in mind the respective directions of the forces and of the acceleration.

B) Objects in a system linked together in a way so that they all accelerate and move together can be treated in a sense as a single object with a single mass equal to the sum of the masses in the system and accelerated only by external forces. The forces internal to this system cancel each other as far as accelerating the total mass is concerned. This is because the force of one object in the system on a second object in the system is equal and opposite to the to the force of the second object on the first. Thus they make no contribution to the net force on the system as a whole.

However, once you have you used the external forces on the system and the total mass of the system to help you establish the acceleration of the entire system, and thus each object in the system, go back to Note A above to find the internal forces such as tensions in a cable connecting two objects in the system.

To those interested in medicine.

There is a program for doing something like internships with doctors over the summer. I don't know much about it other than some of my students in the past thought it worthwhile. It is expensive but some aid may be available. If you are interested let me know by email and put NYLF in the subject line.

Honors Assignment and Quiz

This assignment for tonight should reinforce what we accomplished in the last two days:

http://h1.ripway.com/DrCherdack/Worksheet%20F9-92-09.doc

Get all your force homework up to date. You should fix everything turned in so far, but you don't have turn it in again.

The quiz is this Thursday.

Honors Lab on a=F/M

1) It has been pointed out to me that I never defined mechanics. While this is an overstatement, I'll say here that mechanics is the study of forces and their effects, on bodies, and structures. Mechanics quantities include position, velocity, acceleration, force, mass, etc.

2) Item 9 in the lab sheet asks you to use your graphs to find out if the purpose of the lab has been accomplished. Ignore all the words in parenthesis, they are from an earlier version.

AP Relative Motion Sheet

Here is the revised Relative Motion WS. Use this tonight.

http://h1.ripway.com/DrCherdack/Relative%20Mot%20WS%20RM9-09.doc
Here is a key correction to problem 6 from this new version that corrects the error in the old work sheet


6. A ball is thrown from a car heading north at 20 m/s. From the car the ball appears to be heading forward at a 45 degree angle at 15 m/s. What are its vertical and horizontal velocity components wrt the car and wrt the earth?

AP Worksheet 3

Sorry guys. Here's the link
http://h1.ripway.com/DrCherdack/Unit_2_Worksheet_3.doc

Honors Secton2

I spend my weekends grading your labs and reviewing homework. You did not pick up material from the outfolder. Starting Wednesday labs will receive -5 points for every day left in the out folder.

AP Vector Lab

Purpose was to show graphical addition of vectors, i.e., tail to head method, worked and was commutative. We assumed, for now, that the three force vectors should cancel since there was no motion. When B+A = -C and A+B looked just like B+A and A+B+C =0 this seemed like a pretty good demonstration that tail to head worked and was commutative.

Many of you did not add vector C to vector (A+B) as requested in paragraph B. All you had to do to find A+B+C was transfer vector B so its tail lay at the head of vector A and then transfer vector C so the tail of C was at the the head of vector B, that is the vector B in its new location. The vector A+B+C was a vector starting at the origin and going to the head of vector C in its new location. It should have been very small or even zero in magnitude.

Some of you did not provide any sketches at all. You will have to do them to get a grade.

A few of you added vectors as if they were simple numbers. This is very wrong. A force of 3 N to the left plus 3 N to the right = 0N not 6 N. A force of 2 N to the northeast plus a force of 2 N to the northwest = 2.83 N to the north not 4 N north or anywhere else.

Honors Physics Topics Groups

By Tuesday have a name for your group. Something that you can start building some enthusiasm around. A simple example is the "The Magnetics" for the electricity and magnetism people, or the "The Surfers" for the ocean waves guys, or maybe this is more appropriate for the TV group. Also, start thinking about a logo. Last year two groups even made tee shirts with their logos.

Speaking of last year: Hi to Ashley, CaCarly, Amber and Neel.

Labs in General and Torque Lab

All of you should read all of this this because AP will do this lab soon.

With few if any exceptions, the purpose of a lab in our class is to test the truth of a theory or hypothesis or more than one hypotheses. It is NOT to gain experience in balancing, it is NOT to study the effects of moving a balance point , it is not to educate you or give you a feeling of accomplishment. It is to see if something, usually a pretty specific something, is true.

The reason for me requiring you to do a lab, or my purpose for you doing the lab is another matter, and may be something really sinister, such as getting a teenager to think. However this is not the purpose of the lab in itself. It is the purpose of the lab itself that you must put in your report, not any of my or your ulterior motives (which in your case may be simply to avoid getting yelled at by an irate physics teacher.)

Similarly, the conclusion must contain a direct answer as to whether or not the purpose was achieved, i.e was the truth of the hypothesis or hypotheses demonstrated. This should include a restatement of the hypothesis, hypotheses being tested.

For the torque lab, the two hypotheses being tested were

1. Given the definition that torque = Ftangential x distance from point of rotation, then if the clockwise torques = the counterclockwise torques rotational equilibrium is attained,
2. For calculating torque, the weight or force of gravity on an object can be taken as acting on the point which is the center of mass of that object.

Cases 1, 2 and 3 demonstrated the first hypothesis and case 5 demonstrated the first and second.

Question 1 on the torque lab asked about how the sum of the forces = 0. IT said nothing about torque. Many of you made the double mistake of saying the forces were equal on both sides of the pivot. First this was not true, the torques not the forces , were equal. Second the question was not about rotation and torques it was about force. All the weights were downward forces, why did the meter stick not accelerate downward; i.e. what was holding the meter stick up and with how much force?

Question 3 Triple beam; since you never got to use these in chem lab I'll have to explain it to most of you although congratulations to the few who did get this right.

Question 4: your answer should have had a calculation which showed the torque required from mass 3 had to be 4500 gram cm. You could then explain why this was a problem with

M3 = 50 grams and how you might solve it moving M1 or M2 or even the pivot point.

Question 6 should be answered. Write an expression for the ccw torque using 220 g and its distance from the pivot and an expression for the cw torque using 100 g and its distance from the pivot and the mass of the meter stick ( unknown so call it M3) and its distance from the pivot. Set ccw equal to cw and solve for M3. Remember distance is not position, i.e. d not equal x.

Also remember that x means position, not mass, not speed, not force, not torque.

Everyone Meetings

Physics Club ( the coolest club of all) meets at 7:05 in my room (506). Anyone with an interest in physics is welcome.

People who want to participate in Physics section of Science League should meet with Mr. Gilmore at 2:30 tomorrow ( Thursday) in Room 502.

Honors : Net Force

In doing the work sheets remember that we were a little sloppy in class. Its not F = Ma it's Fnet = Ma or a + Fnet/ M. For example, if I have a 2 kg mass being pushed by a 4 N force to the north and an 8 N force to the south, the net force on it is 4 N to the south and the acceleration is 4N / 2kg = 2 m/s/s to the south.

Remember the force of gravity, i.e. the weight, = Mg and is down and has to be taken into account when figuring out what the net force is.

Grades

I have just finished posting your grades so you should be able to see them in the High Anxiety Creator (HAC).

Note the following.

1) AP s: If you have no tests grade I expect you to be taking the retest on Wednesday. If you don't plan on doing that, let me know. If you do plan on taking the retest you need to have attended at least one extra help session between Thursday and Wednesday and you must have at least a 95 in homework on Tuesday

2) Honors projects: everyone got 100 so far if they turned in project choices. Three in Honors 3 got zeroes.

3) Homework see me if you take exception. We did lose some data last week. Lots of technical problems and a few human ones.

4) The overall grade posted by HAC IS NOT YOUr TRUE GRADE. Just look at the individual categories. HAC cannot provide customized weights as I do.

5) Focus on learning and understanding and doing the work and the grades will take care of themselves

E mail and Honors Topics

Our beloved email system will not send emails from me. I can only receive right now. I now have topics from all but D'Arcy, Lefler and Kauffman. I have assigned topics to everyone.

Honors Assignment Schedule

Here is your schedule for unit 2 forces and acceleration

Read the previous post. It also won't hurt for you to read Monday's assignment tonight.

http://h1.ripway.com/DrCherdack/HonorsUnit2Sched10-11Force.doc

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

http://h1.ripway.com/DrCherdack/Force%20Worksheet%202.doc

http://h1.ripway.com/DrCherdack/WorksheetF-2Hnr.doc

All students Rates of Change, Velocity, Acceleration

A rate of change is the amount a quantity changes divided by the the time it takes the change to occur. More formally this is the rate of change with respect to time.

For example, velocity is the rate of change of position. It equals change in position/time it took to move or

or v = change in position/change in t

One can take a rate of change and the time and use it to find the change in a quantity: change = rate of change * time it took

For example change in position = v * change in t [* means multiply]

Velocity is not constant if uncancelled forces are present (net force actually). The rate of change of velocity is called acceleration, a.

a = change in v/ change in t change in v = a * change in t.

An example of this is a book on a table, the table pushes up on the book as hard as gravity pulls down on it so the forces cancel. Take away the table and it falls, but not at a constant rate. It starts out with v initial = 0 and then falls with increasing velocity falling faster and faster until it hits the floor and the floor's upward force stops its motion and cancels gravity. Do you think the force on the book when it first hits the floor is much greater than when the book is at rest on the floor? Think about it. Did the floor create a very large change in the book's velocity at first. Would this require a large upward force?

AP Clarifications on Homework Schedule

Vector Worksheet2 is just Unit 2 Worksheet 2. The answer for problem 3a is 7.51 deg above the x axis. The MS Word document lost some formatting for symbols.

Honors Project Topics

I am still missing topics from several students in Honors 3 ( 7th pd.)


D'Arcy, Christopher Samuel
Harada, Kathryn Yuki
Kauffman, Erica Allison
Lefler, Joshua Patrick
Tobia, Jacqueline Grace
Trentesaux, Adrien, Damien
Tuohy, Shannon Simone

If I do not get email from you by noon Sunday (today), I will assign topics and deduct credit.

All students Location Assignment

I would like to know about where you live so I can organize project and study groups in each class. Please go to maps.google.com and look up Basking Ridge. Find your home and print out a map with your home on it. I don't need your exact location but get it within about 1/5 of a mile or so. Write your name neatly about where you live. Bring it in Monday. You don't have to use google if you have another source for the map.

If you think this is too invasive just send me a note and I'll try to assign you to a group some other way.

Labs

All labs should have your name; section number or period; date the lab work (not the report just the data taking part) was completed and the lab partners at the top, even if the lab sheet doesn't have a space for these things.

Again, ALL labs must have a purpose section and a conclusion section.

Honors labs on torque are due Tuesday.

AP Labs

1) Falling mass lab.
Its formal
Note that you cannot find the value of the last two columns for the first row because you do not know what v zero was ( it was already moving by the zeroth dot.)
Plot the cumulative distance (when I said plot the displacement , I meant the displacement from the origin which is the same as the position).

2) Vector lab. Section 5 due Tuesday, Section 4 due Wednesday

I did not show Section 5 how to move a vector from the origin to the head of another vector while maintaining its direction, so I'll try to explain it here. Let's say you want to add vector A to vector B. Thus you want to draw a line that is parallel to vector A, which starts at the head of vector B and is just as long as vector A. Take two rulers or other objects that have straight sides and ends at right angles between their sides and bottoms. Place the first ruler so its edge lines up on the vector you want to move, let's call it vector B. Place the second ruler so its edge lines up with and fits snugly against the bottom of the first ruler. Hold ruler two firmly so it doesn't change orientation. Now slide the first ruler keeping its bottom tightly against the second ruler's edge until the edge of the first ruler lines up with the head of vector B. Use this edge to draw a line which will be parallel to the original vector A. The new vector A will be on this line starting at the head of vector B and equal in length to the original vector A.

Every lab needs a purpose and a conclusion. The vector lab should have these plus two diagrams ( B+A and A+B+C), and answers to the questions directly on your lab sheet.

All labs should have your name, date the lab work was completed ( today in this case) and the lab partners at the top, even if the lab sheet doesn't have a space for these things.

Honors Project Topics

I need to have project topics from the following people, either you did not submit them or I missed noticing them amongst the other homework you turned in. E mail me your topics by Sunday morning so I can get your groups established. If I don't get an email from you, I will assign you to a group and you will also lose some credit. Please do not let this happen. Have a nice weekend

D'Arcy, Christopher Samuel
Harada, Kathryn Yuki
Kauffman, Erica Allison
Lefler, Joshua Patrick
Tobia, Jacqueline Grace
Trentesaux, Adrien, Damien
Tuohy, Shannon Simone

AP Section 5 Lab

You were asked to leave your setups and rulers in place , but told to return the scissors and string to their respective storage places. The string and both scissors were left out. Next time the offending group or groups who do not follow requests for cleanup will lose one letter from their lab grades.

AP Assignments

Here are corrections to the schedule for home work due Monday and Tuesday



For Monday 9/20 Read Section 3.7 Do problems

47, 20, 31, 63

For Tuesday 9/21 Do Unit 2 Worksheet 2 prob1 and 2; Chapt 3 prob 51, 68, 69, 75

For all about Labs

Using today's vocabulary, formal lab reports are the default. Formal labs are required unless you are supplied with a lab sheet from a manual or unless I explicitly tell you otherwise. Even with a manual sheet you need to supply a purpose and conclusion.

Just answering questions provided in my labs is not enough for analysis and discussion.

See the course guide for what is required.

Honors

Go through the lab. Make sure your errors are less than 2%. If not see me tomorrow.

Be ready to finish it quickly tomorrow, i.e. take much less than one period. Remember you need to do only through case 5c to complete the lab. For case 5 make sure you understand that one of the torques is provided by the meter stick itself. In case 5a we analyze it assuming that all the mass of the meter stick acts at the original balance point (very near 50 cm) . Does your analysis for 5a provide an acceptably small error?

(From now on we are assuming you are facing the meter stick with 0 on your left and 100 on your right)
For case b analyze it by treating the meter stick as two pieces but ignore the piece on the short i.e.left side (this is obviously a mistake so we should get a big error). The large piece has a mass = total stick mass x (100cm - the new pivot point)/100cm, i.e. that fraction to the right of the pivot. This mass acts as if it was all located at the middle of the piece of stick to the right of the new pivot point, ( this should be somewhere around the 65 cm mark or more precisely at: new pivot + 1/2 [100 -new pivot]). This will provide a clockwise torque. You will probably get a 20% or so error for 5b.

For 5c you start with 5b and then add the torque from left side of the meter stick in to the counter clockwise torque. The left side has a mass of total stick mass x (new pivot/100). The torque is as if all this mass were at the center of this piece of this part of the stick i.e., at new pivot /2. Adding this counterclockwise torque in should get you back to pretty low error.

Honors balancing WS Solutions

Here are the solutions to last Friday's work sheet. If you don't understand them come see me.


http://h1.ripway.com/DrCherdack/BalancingWS1slns.doc

Honors Assignment

Your assignment for tonight is twofold.

1) Write a clear purpose for the torque lab. Remember why perform labs ( experiments) in this in general.

2) I hope that many and perhaps most of you now understand a lot more about torque and balancing, so your assignment is to go back and do the problems you couldn't do before. You should be able to do all the problems from the in class worksheet (especially the last one with the off center meter stick), the book stack problems, and most of the book problems. Section 3 (7th period) should all be able to do the piano and beam problem from the book. Section 2 should try it again, and we'll go over it tomorrow.

I'll post the solutions for the in class problems soon

AP Quiz

For tomorrow's quiz expect to find the 3 equations relating displacement to vs, a and delta t given on the test. However, you must know the definitions of displacement, v, and a. You should also know how to find delta t if given delta x and v avg or if given delta v and a. You should be able to get expressions for v final or v initial or t using the delta x = (vf^2-vi^2) /2a as a starting point.

Honors Assignment

Read the Torque Lab and try your best to do the Advanced Study Assignment. We'll talk about forces tomorrow. Wednesday and Thursday wear closed shoes, we'll be using hanging weights.

AP Unit 2

Here is your new schedule and materials for 2 dimensional motion, vectors, and relative motion. Life is good, right?

For the lesson for 9/20 on your schedule, please change Constant y to Delta y =0.

http://h1.ripway.com/DrCherdack/APUnit2Sched10-11.doc


http://h1.ripway.com/DrCherdack/Unit_2_problem_sheet.doc


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

http://h1.ripway.com/DrCherdack/Relative%20Mot%20WS%20RM10-08.doc


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

AP Text Book Problems

Many of you did not get the purpose of the some of the Chapter 1 problems. The point was not to get numerical answers, but rather to develop a visual and intuitive understanding of motion. Perhaps you did not "get it" because I didn't really cover it in class.

For example, Problem 37 would show downward arrows of increasing length as the melon descends. The space between successively lower points would become larger. In problem 40 the problem with the wad sticking to the ceiling required you to show a series of vertical arrows depicting the motion of the wad as it rose toward the ceiling. Since the arrows indicate the velocity, each arrow should be vertical and smaller than the one below it since the wad is slowing down at the rate of 10 m/s for each second. Similarly the successively higher points would become closer together as the wad slows down.

If you can't resist the temptation to come up with numerical results take a look at these: For 37 we have vi and a and displacement so the answer is

square root (2 a displ+ vi^2) = sqrt(2(-10)(-10)+0) = 14.1 m/s

For 40 we have delta t = [+sqrt (2(-10)(3) +100)-10]/-10 = .37 sec or there abouts.

General Information on How to do Physics and other sciences.

I believe that the scientific method begins with intelligent observation of physical phenomena. For a hypothesis to be accepted as true it must be tested physically. Mathematical derivations, elegant logic, strong convictions are not enough. Nature has the final say.