Honors Practice Problem #9

The torques = F per arm times distance of arm from axis of rotation x 2 arms per turn x # of turns.

Using force per arm = ILxB I get F = 2X.125 X.048 = .012

Distance to axis of rotation = 1/2 a side = .125/2

torque = .012 x .125/2 x 2 arms x 75 turns = =.00075 x 2 x75 = .12 Nm or answer C [ not D]. Check me and see if you agree.

Honors Quiz and Homework

Quiz on magnetic fields and magnetic induction will be Thursday.

Homework, or the lack of it is becoming alarming. The next step will be messages home.

Permanent Magnet Lab

Unless you have received a specific waiver from me, such as because of absence and need to do the lab, the last day to turn in your "strength of a permanent magnet" and receive any credit for it is Wednesday. See the post from 4/25 for details about your report

AP MC#1

The answers to MC #1 have been removed

AP Modern Physics

Here is  a more recent version of the summary of modern physics. 

Note that the Davisson Germer experiments involved electrons beams incident on crystals and scattering off  them (not electrons passing through slits)  in ways that showed wavelike interference patterns, confirming de Broglie's hypothesis about particles behaving like waves.

ModernPhysAPSummary08.doc

AP Tests and solutions

The good news is that several of you got high or perfect scores on the refraction problem.  Unfortunately that is all the good news.  

Adding a weight on top of a piston adds to the original pressure and compresses the gas. If the gas cylinder is in a water bath of fixed temperature, the gas temperature does not change appreciably, i.e. the processes are isothermal. Since T doesn't change then PxV is constant so 

Vnew = Vold x (Pold/Pnew). 

If the pressure, P, is held constant during a process, its isobaric and since PV = nRT and n and R didn't change  we have 1= Vnew x P /(nrTnew) = Vold x P /(nRTold). Canceling  n and R, multiplying by Tenw and cancelling the Ps which are equal in isobaric processes, we get 

Vnew  = Vold x (Tnew/Told)

No one seems to know how to use a volt meter despite having taken over 100 measurements with voltmeters. [You do not insert voltmeters in series with circuit elements. They measure the voltage difference across an element, i.e. the potential difference ( also known as the voltage difference)  between two different points in a circuit.]

Some of you seem to think that a single deuterium nucleus has a mass of 2 kg. An atomic mass unit is 1.66E-27 kg not 1 kg. Most of you never got that far.  

Here are somewhat rough  solutions for all of FR 2001. We will go over MC 1 in class tomorrow.

FR2001Solns.PDF

Honors and Mathematical Magnet Lab and Homework

Your lab reports are due Monday. This is a formal lab. The purpose was to measure the strength of the permanent magnet. Describe the process and the method used to find NI and B pm carefully. Then give your results. The manufacturer claims a strength of about .5 T so the error was very large. Try your best to really analyze this.

Mathematical: all Unit 13 homework is due Monday or never. Also, no more Friday breaks unless all homework is in Monday except practice problems which are due on Tuesday.

Note to Honors and Mathematical DO ALL practice problems except #5 which is extra credit.

Mathematics Quiz

Yesterday I posted a request for you to return your currents lab quizzes from last Tuesday. I received none.

If I do not get them back on Monday you will lose significant points.

AP Students Schedules

Send me your AP test schedules immediately. I MUST know what days you will be out the first full week of May.

The recent test results indicate we have a great deal of work to do and some of it must be done outside class hours.

Rutgers Astrophysics and Columbia Honors Science

The Rutgers astrophysics program is a great opportunity to do real research using the same data that leading astrophysicist are using to analyze super nova explosions, black holes and other sources of very high energy emissions in space.  Here is a chance to do real science with close contact and support of faculty in a way that only graduate students usually benefit from. 

The Columbia Science saturday is another really valuable program that you science types should consider seriously. You can find links to both on this download


Extracurrphysicsprog.doc

Mathematics Quiz

I need to confirm the grades for the quiz from this past Tuesday. Please turn them back in tomorrow and remind your classmates to do so.

Thanks,

Dr. Cherdack

AP Objectives, Homework and Tests

You are missing four pages from your objectives handout. 2 pages following 13 , a page following 16 and a page following 20. When you pick them up tomorrow note where they go on your current pages and fasten the additions to the end of your package.

Your homework for tonight includes a description of the photoelectric effect. You should provide a general description, what major aspect of modern physics it demonstrates and discuss the quantities: stopping voltage, work function, threshold frequency, electron kinetic energy, and how they are related. Show a typical stopping voltage vs frequency graph. It must be legible. It will count as 5 points toward your quarter grade!

There will be a practice AP test tomorrow. It will be multiple choice or free response. It will comprise 50 % to 60 % of the real thing.

In addition you will receive one free response and one MC as homework for the weekend. You will receive additional practice tests in school and for homework and in class next week. When you identify your weak spots come in for extra help.

Particularly for Free Response Tests, you must not STOP. You must try to solve them. There will be no one to ask on exam day. You can start a problem without knowing all the steps to complete it. What you have to do for step 2 may not occur to you until you try step 1.ALWAYS write the question, usually in the form of : quantity wanted =?. Thn write the given information. Then write the relationships between given and wanted quantities. Often there will be additional unknowns in the relationship between given and wanted, but there will usually be other relationships to get you from the given to these additional unknowns.

As an example, you need to find acceleration. You are given distance and initial and final speed but not time. a = (vf-vi)/delta t. d is given but delta t is unknown. Find delta t from delta t = d/vavg using vavg from (vi+vf)/2. Three steps to find a but you can do it. [Some of you might use a =(vfsqrd-visqrd)/2d but that is beside the point here]

AP Lens Lab

Nicole, Ryan, and Kuba should come in tomorrow before school to redo the last two steps of the lens lab.

Labs for All

AP Lens labs are now overdue. You have one more day to get them in or nothing.

Current labs Honors and Mathematical, Thursday or lose points, and by Friday or not at all.