AP MCs

Scores on the in class MC tests are pretty good, with both classes averaging in the mid 4s. This does not mean you can relax, yet. You must get to the point where you will be very comfortable when you walk into the test on May 11, i.e., you must get fluent in the subject

It would be really nice if you could see what you got wrong on the 2 take home AP tests, but I won't release your scantron until I get an email from you.

Honors and AP

Grades are posted on the Home Accident Center. Let me know if you think something is wrong, i.e. different from what you have earned.

Honors

Let me know by email if you want to continue with waves through sound and light waves and then go back to fusion, or you would prefer to go back to fusion and return to waves later. I will follow whichever the majority of emailers call for.

AP

You get a break tonight, but you should bring your FRs from the last two nights up to date if you haven't already done so. Also look over the MCs in your possession and email me with topics you want to cover.

Honors Assignment

In addition to tonight's assignment, clean up all the previous assignments on waves. You need to be competent with both traveling and standing waves. Know how to find lambda, c, and, f including for different harmonics; know what affects wave speed and lambda; know how a change in medium affects a wave; know how interference ( constructive and destructive) works; know how to write displacemnt as a function of time and position.

Invention contest

If you think you are inventive, take a look at this folks. Let me know if you are interested.

http://www.popsci.com/files/SchoolEntryForm1.pdf

All Students Great Adventure

Forms and and $50 due by May 8. If you have a season pass ( you are obviously spending too much time and money on frivolities and can expect no mercy about late labs and homework), the cost is reduced to $27.50

AP Pair production

Please make sure we cover pair production in modern physics.

Note: It has nothing to do with arranging prom dates.

More on the AP MC

I don't mean to impugn anyone's integrity about the MCs. After all, I did say in my instructions, complete the tests after you finished taking them as practice tests. I just want to know how I should treat the results you turned in. Are they a true indication of what you can do on a real test, or are they the result of your best effort including outside resources.

AP Assignment and MC Test

1) Section 4 Do 1-3 of FR 2007 Form B for tonight. Section 3 just do 1 and 2 of FR 2007 Form B and study for MC.

2) Section 4 did pretty well on the MC test today. Section 3 will have to study a bit to do as well

3) Homework MCs. It is apparent that several different attitudes were in play about this test. Some took it as a practice test. Some took it as just homework and obviously had books and notes open while they took it. Some apparently decided to see how ell they could do without reading the question and I am sure in at least two instances that someone took tests different from the ones I created answer key for. I would like an email from everyone who did not follow the rules for test taking ( i.e. got help from more than their memories and official info sheet) when doing the MCs informing me that this is the case and that I should not treat it as a take home test. Integrity is important.

Honors

1) Section 2 Period 6 is very seriously behind in getting labs and homework in. Wave labs after Wednesday are zeroes. Homework is averaging about 80% and your grade will reflect this. The wave assignment from the break was critical and the many of you who failed to do it have gotten much less out of the last two days than you would have.

2) The section 3 labs on harmonic motion were not impressive. Many contain fundamental errors, including some showing utter disregard for simple logic or algebra. While many in section 3 have turned in the wave assignment and the wave lab, the rest of you are facing dire consequences. Also, many of the assignments turned in show largely consistent mistakes in many areas. The information needed to do the assignment is in the notes. Therefore you must review the notes and learn and do the assignment correctly.

AP Assignments etc

1) Your assignment for tonight is FR 2006 Form B problem 6 and FR 2006 problems 1, 4, and 6

2)We will be taking a full blown MC test portion on Wednesday for Sect 4 and Thursday for Section 3. Bring your info sheets

3) You don't have to worry about relativity for the AP test. They don't seem to think it's important.

Honors Schedule for Waves Unit 12

Here is the new unit schedule and a home work set

http://h1.ripway.com/DrCherdack/HonUnit12%20Wavessched09.doc

http://h1.ripway.com/DrCherdack/HmwrkonOscillsWaves2-08.doc

AP and Honors

When looking at induction of voltage in a coil, turns means means number of wraps of wire in a coil not how many times a coil rotates in space.

AP and Honors

With the AP exam approaching, I will be reviewing AP material every afternoon for which students show up this week and next. Honors review can occur Wednesday, but if an AP group shows up, they get first priority.

AP Practice Tests

Make sure you have 2 copies of your results, both MC and FR. One we can review in class, and one you can turn in. Both should show enough work for you to understand what you did right or wrong and for me to see you really did the work. Remember, home work is a big part of your grade for this quarter.

Honors Projects

Plasma, electrical, thermo, and magnets groups all have  along way to go to meet their goals. Review the information you need to complete your system designs.

AP Mirror Problem

You may recall the book problem where someone enters a room 15 feet wide with mirrors on the left and right walls. She stands five feet from say the left wall and faces it. The question is how far from her do the first three images of herself appear. Her first image appears to be 10 feet from her: 5 to the mirror and the image appears to be 5 feet behind the mirror. When I solved it for her second and third images I got 40 feet and 70 feet for the answers. This differed from the books answers of  30 feet and 40 feet for the second and third images. In all cases I was considering the image of her front.

A couple of students have suggested the following explanation. The second image is not of her front, but of her back! The image of her back must travel 10 feet to the right wall and then 15 feet to the the left wall so it appears to be 25 feet behind the left wall and thus 30 feet from her. The third image is of her front and corresponds to my second image.

In any case the images beyond the first would barley exist, since the girl's body would block most  rays from the right mirror from reaching the left mirror and those from the left mirror from  reaching the right mirror.

To All

Today is a very special day its the birthday of Missy Nwokonko . 

Sorry Missy: I didn't want to shout about it. Happy Birthday to a really nice person

AP Modern Physics

The summary of modern physics posted on April 10th is full of good stuff. Make sure you go through it.

To All Urgent

Here is an announcement for an open house this Saturday at NYU Polytechnic 

http://poly.edu/admissions/undergrad/events/index.php?id=357 

and one for their construction management program - see  end of post

You can RSVP and obtain additional information about the Spring Open House activities at http://poly.edu/admissions/undergrad/events/index.php?id=357 or just show up at the door.  We are located in the MetroTech Center at the heart of downtown Brooklyn, hardly a few minutes by car or subway from the financial center of New York City and NYU’s Washington Square campus.

 

         Or, contact Prof. Chiarelli directly.

 

Prof. Lawrence Chiarelli, PE, Esq.

Polytechnic Institute of New York University

Department of Civil Engineering

Center for Construction Management Technology

6 MetroTech Center

Brooklyn, New York 11201

(718) 260-4040

(718) 260-3433 fax

(201) 655-3877 cell

LChiarel@poly.edu

http://www.poly.edu/construction/undergraduate/index.php. 

Honors and AP

Here are notes and problems on waves. Required for honors. Recommended for AP. 

You do not have to read section 7 of the notes on waves, but make sure you have wave speeds  under control from the other notes on wave speeds.

http://h1.ripway.com/DrCherdack/Notes%20on%20Waves4-09.doc

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

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

http://h1.ripway.com/DrCherdack/ProbWvs4-09.doc

Calculator

Someone left a nice calculator on a desk in 506 a couple of days ago. Come claim it.

AP Optics

Remind me to show you the half a lens is better than none demo

AP Pratice Exam Assignment

Make sure you pick up the two multiple choice tests on Friday. DO NOT MAKE ANY MARKS ON THESE EVER.

Go to AP Central and the Physics B homepage. Get the 2000 through 2003 FR ( don't get the form Bs). Take the 2000 FR as a real practice test with the MC marked as #3. 90 minutes for the MC and 90 minutes for the FR. After that go and complete the tests. Then do the 2001 and 2002 FR as homework. Then take the 2003 with the MC marked #1 with big U as a real. That means 90 minutes for the MC using only the info sheet no equations and no calculator. Then take the FR 2003 for 90 minutes with equation and info sheets and calculator. You need to turn all this in to be entered ( and marked) for homework. Answers must be on clean sheets. Make duplicates of your work so we can review in class while your papers are still being entered and reviewed. You must show real effort.

Do not be easily discouraged. We will practice with several more tests and a 70% correct is a 4 or 5.

Honors Quiz

Sorry guys, but it will be a bit longer than I originally intended.

If I were someone whose teacher spent the last few days on reviewing a certain homework assignment and a lab about oscillators, I think I'd make sure I knew about the main ideas covered in the homework and lab really well. What do you folks think?

All students

I am still trying to track down some of my books. Please bring anything of mine you have in by Thursday.

AP Unit 15 Updates

Here are a new Schedule and problem sheet. The problem sheet is now on the schedule as is the delay in the quiz. The problem sheet has answers but they are the product of a late night and haven't been checked yet.

http://h1.ripway.com/DrCherdack/AP%20Unit15%20ModPhys%20schd09r1.doc

http://h1.ripway.com/DrCherdack/unit%2015%20probsheet%20r4-09.doc

AP Optics practice

Here are some examples for you to practice drawing ray diagrams and calculating dimensions


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

AP Period 4

Please return your optics test to me ASAP. There may be some extra points in it for you.

AP Modern Physics Quiz

Out of the unlimited generosity of my heart (and since so many of are going on the Calculus field trip). The modern physics quiz will be postponed until Friday. If this doesn't get me a new car ( or at least a recent used model) from you cheapskates I just don't know what will.

Optics

Many of you have not mastered ray diagrams. It is clear that if you are among these individuals, that you have not learned as I hoped from the notes I provided. You alone  know if this is from failure to really read the notes, or from inability to get the basics down from reading the notes. If you have tried using the notes and still need help, see me. If you haven't tried the notes, do so ASAP.

Missing Books

Several books were borrowed over the past year including, but not limited to, an Electrical Engineering handbook several other books on electrical engineering and two copies of books on black holes. Please bring in all books you have borrowed from me.

Honors Period 9

It is my understanding that many of you chose to play with the plastic slinkies on Thursday. Now the room is filled with empty boxes. The slinkies must be returned and put back in place.

1) Snel's Law lab and 2) critical angle

1a)  Many of you stated the purpose of the lab was to demonstrate Snel's Law and then failed to write Snel's Law anywhere in the lab report. This is carrying brevity to fault.

1 b) Even though the lab sheet has Snel's Law as n = sin theta 1/sin theta 2 this is true only when medium 1 is a vacuum or a diffuse gas such as room pressure air. The correct formulation comes from the fact that sines are proportional to the velocities so that 

sin theta 1/sin theta 2 = c1/c2 = n2/n1.

2) The  critical angle occurs when light in the denser medium totally reflects off the interface with a less dense medium.  The critical angle is when the light trying to enter the less dense medium bending away from the normal bends to an angle of 90 deg from the normal. Thus sin theta less dense = 1 since sin 90 = 1. Using results from above we have

sin theta more dense/sin theta less dense = n less/ n more  or 

 sin theta critical /1 = nless/nmore

which also gives n more = nless/ sin theta critical

Topics in Physics

Proposals are due Monday 4/13; First Outlines are due Friday 4/17;

Annotated outlines with full subtopics with brief summaries per subtopics and biliographies are due Monday 4/27

All students Faraday Induction

Many of you exhibit confusion about number of turns in a coil. This is the number of "wraps" one makes in creating a coil. It is not the number of rotations the coil makes after it is completing. So do not confuse turns, made in manufacturing the coil, with rotations or the number of times the coil revolves completely.

AP Schedule for Modern Physics

Here is the new schedule and the notes ( review) and summary you need to go through this weekend, See schedule for points to master. Also see your list of topics ( that 21 page list with check marks in columns) for more guidance on modern physics topics to study.


Also, complete problem sheet by Thursday.


http://h1.ripway.com/DrCherdack/AP%20Unit%2015%20ModPhys%20schd%2009.doc

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

http://h1.ripway.com/DrCherdack/ModernPhysAPSummary08.doc

http://h1.ripway.com/DrCherdack/unit15probsheetrnc.doc

Honors Assignment

Here is your schedule etc. for harmonic motion ( oscillations).

http://h1.ripway.com/DrCherdack/HonUnit11harmsched09.doc

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

http://h1.ripway.com/DrCherdack/unit9problemsheetr1.doc

http://h1.ripway.com/DrCherdack/RevProbRotandHarmR2.doc

AP 2 mirror problem

Here is my take on the two mirror problem Ch23 #1. The book seems to think that one only needs to consider how far the second mirror is behind you (ten feet) and you add this 10 ft distance to the initial 10 feet between person and his first reflection once for each additional reflection. 

I don't know where this reasoning comes from since the source of the image in mirror 2 is a reflection from mirror 1 . My approach is to construct the straight path of the ray of light that hits the eye back to where it originates including all the reflections.  See if you accept my reasoning or tell if I missed something.

http://h1.ripway.com/DrCherdack/2Flatmirrapprnt%20dist.doc

AP Parctice

AP Exam Practice materials are due Monday, don't forget. See earlier post for detailed instructions.

Honors Assignments and Group Goals

1) A new schedule will be posted by Friday

2) Plasma group period 6: Someone go to 407 and pick up xeroxing. Take 3 copies and mark the other 3 for plasma group and place in Honors 3 ( orange) outfolder.

3) Have group meetings tomorrow: Here is an updated version of the presentation Goals from last quarter. See that you can fulfill them.




Group Presentations: You must explain things in a way that shows you have gained understanding and will help the rest of us do the same. Cut and paste recitations from web pages etc. are not acceptable. Minimum 20 minutes ( that's not 5 minutes plus 15 minutes for questions).
Thermo group on work in your cycle, just the main points for isothermal, adiabatic and isobaric expansions. Can discuss regenerative feedwater heating if you really understand it. Need actual cycle values including flow rates, temperatures, enthalpies, at all points of cycle


Plamsa group drift, tansport and JXB = gradP

Magnet group, superconductivity, coil dimensions, coil currents actual values, coil features, conductors (materials) and forces.

Electric power Group: Farraday induction, conceptual design of turbine : field coils, stator coils, exciter; number of field poles, number of stator coils (windings) size of coils, currents and volts, strength of magnetic fields.

Heating group: description of ion source accelerator grid, neutralization chamber; beam dump. Provide design info such as size, voltage, energy, actual operating pressure. Use ITER as a basis, but you must understand what you are talking about.

Honors thermo quiz solns

Version I C,B,A,D, 4 x,9.5 E24, 1) 72 m3; adiabatic 1192 m3; 344 K; -1.4 E9 J; +1.4E9 J

Version II a,d,c,b,1.5 x, 9.66 K 1) 149 m3; adiabatic; 5.57 E5 Pa; 404K; - 1.57 E9 J; +1.57 E9 J

Honors Assignment

For tonight Section 2 carefully review lab sheet; you'll need to do it all in one period tomorrow.

Section 3 start processing your data and creating your graphs and using slope to find k for parts one and two.

AP Practice Test Homeworks

For this quarter homework will make up about 40 % of your grade. Most of that, will be practice tests for homework. Do it on time and turn it in.

Tomorrow, make sure you pick up two MC sheets comprising the last half of the test you began near the end of March and the 1999 FR. They are to be completed by Monday. Answers are to be on clean sheets. You must show work for the FRs. Keep the questions and mark your answers on them for when we go over them in class.

Follow this procedure for all homework practice tests.

Honors Assignement

Read the Notes  and then do the following problem.

A mass of 2 kg is attached to a spring which has a  spring constant k of 50 N/m. The spring/mass assembly is horizontal and is supported on a frictionless, what else? table. The weight is pulled ( by You) to the right until the spring is stretched .2 m. What is the force the spring puts on the mass. What is omega? What is the potential energy stored in the spring (g and h don't enter into this at all). What is the acceleration of the mass when you let go. What is the maximum KE of the mass. What is the maximum speed and where does it occur? Let x = 0 when the spring is relaxed. Assume the spring's mass is negligible.

.

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

AP Ch 22 Problem 3

I was pleasantly surprised when I found a problem actually asking for angular speed, omega, in your text. I might have know they would mess it up. The answer they gave was the frequency, about 500 Hz. The angular speed is of course 2pi times as great.
The solution uses the idea that it makes one eighth of a rotation in the time it takes light to travel 35 km out and 35 km back. This is about 2.33 E-4. so frequency = 1/8 x 1/2.33E-4

All Juniors Scheduling

I have received word from a guidance counselor that Level V Honors courses are not available to seniors. You may take only CP or AP Level V. Tomorrow, someone can let me know what Level V means

HonorsThermo quiz Quiz

Here is the link for the Thermo quiz. Assignment is as posted yesterday.

http://h1.ripway.com/DrCherdack/HnrsthermoquizB09r1.doc

AP Geometrical Optics Unit 14 Schedule

Here are new schedule and worksheets. Note the quiz next Thursday. The notes and summary for geometrical optics were posted March 30. I've posted the modern physics stuff you'll need later here.I also threw a couple of separate derivations you can look over.


http://h1.ripway.com/DrCherdack/APUnit14BLightsched-09.doc

http://h1.ripway.com/DrCherdack/Unit14problemsheetr1.doc

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

http://h1.ripway.com/DrCherdack/ModernPhysAPSummary08.doc

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

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

Honors Thermo Quiz

Here is last Wednesday's quiz. Correct the version you took and then take the other version and turn in that version showing all work done neatly on Monday

All Students including Topics in Physics

You first assignment for the new quarter is the following. Print out the following message and return it signed.

All assignments must be turned in no later than the end of a unit, or in the case of labs, no more than three school days after the completion of the lab. No credit for any late work (other than submission delayed by absence ) will be granted.

_______________
Student


_______________
Parent or Guardian

AP Problem sheet

Problem number 10 seems to have a problem. The answer given assumes no phase shift from the reflection of the ray on the soap water interface. I think this is wrong. If Nwater>Nsoap>air both reflections result in a phase shift and so for a destructive interference 2 Nsoap x thickness = lambda/2. This gives lambda longer than the maximum for visible light. If one looks for the next destructive interfernce, it would require 2 Nsoap x thickness = 3 x lambda/2. This puts lambda at the edge or beow the visble light limit.

There may also be a problem for the oil drop problem,#13. I'll try to check it tonight.

Autobiographies

Autobiographies are also required. Must be in tomorrow

Group Reports

Well, I got one reminder to publish the list of group reports from about 80 students.

Here it is. These reports are due tomorrow. They are REQUIRED.

http://h1.ripway.com/DrCherdack/Grpreports4-2-09qrtr3.xls

Group reports

Still a disaster, remind me to publish current spreadsheet tomorrow.

AP Three important items

1) I post a lot items so don't think seeing one is seeing 'em all. Scroll down to older posts.

2) Make sure you go to the gridding fest in the auditorium lecture halls on Tuesday.

3) Remind me to discuss polarization tomorrow.

Thermal Energy conservation lab

I expect, or at least, would like, a brief but formal writeup showing that you know you were trying to demonstrate the conservation of thermal energy. You did this by collecting data and using it in a conservation based equation to determine the specific heat of your sample. If the specific heat came out close to the standard value, it confirms that your equation which was based on conservation of thermal energy was correct.

You should definitely include both the original equation relating loss of energy of the meatl to gain of energy by water/container AND the rearranged equation for cmetal = etc.

Standard values: brass about 390 J/ (K kg); iron 440 J/ (K kg); Aluminum 920 J/ (K kg)

Honors period 6 thermo quiz

I haven't graded it yet, but I'm guessing the results will not be great. Since there were some serious typos on the test, I will allow a mass retest on Thursday if I receive enough emails to warrant it.

AP Quiz

After some soul searching (always a difficult exercise for those of us without one), I have decided to postpone the quiz on wave behavior of light until Friday. It will include gratings and you will have to know something about the electromagnetic spectrum and dispersion. Dispersion is the fact that light of different frequencies have different indices of refraction ( travel at different speeds in matter) so they bend different amounts, thus rainbows and some of the reults from your Snel's law lab.

AP currents labs

A large number of you are laboring under serious misconceptions. Currents flow in circuits because fields are created in conductors which cause the electrons present in the conductors to gain small average velocities. The amount of current that flows depends on the field and on how many electrons are available to move and how easily they can move. The field , in turn, is determined by how much voltage difference is placed across the conductor. Thus the amount of current that flows depends on the nature and geometry of the conductor and the voltage across it. The total current in a circuit is DEFINTELY NOT some fixed quantity, it IS dependent on the number of conductors available to carry it.

Batteries impose a voltage difference across a circuit. The current arises in response to this voltage difference and, once again, depends on the number and quality of the conductors experiencing the voltage. By removing a parallel resistor you have removed a conductor (resistors are just imperfect conductors) and thus reduced the total current. If the voltage remains the same, each remaining parallel elements will carry its own original current. If the voltage available to these elements rises, as it sometimes does because the lower total current reduces voltage losses elsewhere in the circuit, there will be an increase in the current in the remaining elements, but this is NOT because the current from the removed element has to find somewhere to go. The current that was flowing in the removed element simply ceases to exist because the electrons that were flowing in that element are no longer in the circuit.