3rd quarter Grades

I have been in touch with some of you by email about grade changes. For some reason to do with HAC I will not be able to post these changes until May 2. Sorry, I thought I could do it today, but the entries are locked in until 5/2.

This Week

A reminder that I will be out this week as I continue to recover from having a new hip installed.

Honors you have already been told your schedule.

AP will be meeting with Mr. Gilmore's classes and you will be getting a review of magnetism and induction. Do bring in your AP exam break assignments and the modern physics worksheeet posted below. You can work on the green free responses and the modern physics worksheet when you are not working with Mr. Gilmore.

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

Break Assignment and Schedule Change

1) I have received only a couple of emails for the break project assignment each including a meeting report and a real question you would like help in answering. I should receive 42 by tonight.

2) Monday 4/18 and Tuesday 4/19 will be research days. The project work assigned for Thursday is now due Thursday. Wednesday and Thursday will be for doing fluids worksheets. Bring in FD-1 on Wednesday so you can do it in class. Turn in completed worksheet FD-1 on Thursday and FD-2 on Monday 4/25. Here is worksheet FD-2 Please read it before Thursday and bring it to class so that you will be able to do the problems in class on Thursday.

http://h1.ripway.com/DrCherdack/Fluids%20Worksheet%20FD-2.doc

AP MC

Sorry the MC that we did half of in class was MC 5 not MC 4

Honors Schedule and Materials for Fluids

Hope you are having fun during this break despite the weather. Here is your schedule for fluids and for project work . After all, I can't let you have too much fun. Bring all this stuff to class next week, I won't be there so you can do some wotk during class to reduce the homework burden.

http://h1.ripway.com/DrCherdack/HonUnit14Fluids10-11.doc

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

http://h1.ripway.com/DrCherdack/Fluid%20Dynamics%20WorksheetR1%20.doc

http://h1.ripway.com/DrCherdack/Review%20Sh%20Fluid%20DynamicsA.doc

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

AP Assignment:AP Tests and Modern Physics

Do not write on any of the tests. Show work, record free response answers on a separate sheet from what you plan to turn in. This way we can review the tests before you homework gets entered. I'll try to get the scantron back to you within one day. This assignment is worth 8 homeworks.

The two green free response and completing MC4 and doing MC2 or whatever MC you have EXCEPT MCB6, are for free practice and can be done open book or even with help from your group. MC B6 and the white free response ( begins with a roller coaster) are to be done as a simulated exam. The MC should be done in 90 minutes with only the information ( first ) page of your info and equation sheets, and NO CALCULATORS. After a 5 minute break, do the free response in 90 minutes using the equation and info sheets and a calculator. Again this is to be done as if it were a real test. No outside help. Show work on all tests

Here are the modern Physics Links:

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

Honors Project Assignment for Break

Groups should meet at least once and preferably more over break. Each student must email me a meeting report (who when where and what was discussed.) The what should encompass at least two whole real live sentences. Your email also must include at least one real question you would like my help in answering.

Honors Assignment

The assignment from last night (Chapt 10 not 3 ) is due tomorrow. do the assignment below for Friday. Friday will also be a research day.

Read Chapt 10 Sect 5,6,and 7.Do Chapt 10 Prob 11,14, 17, 24, 25

AP Derivation of f = R/2

Here is a derivation of why f = R/2 for a spherical mirror

http://h1.ripway.com/DrCherdack/Derivoffforsphmirrr1.doc

AP Series Parallel Lab

I just finished grading the series parallel labs for AP 4. Every single one of them got most of the questions wrong for parallel circuits and AP 5 wasn't much better. If two bulbs or other resistances are are in parallel they see the same voltage. The current expected in each resistor or bulb is found by dividing that voltage by the resistance of the resistor in question. There is no consideration of the other parallel resistances in this process. As long as the voltage is not altered the current in resistor 1 does not vary regardless of the value of or even existence any other resistor in parallel to it. All of you used this valid approach in calculating the currents in the resistors in part B. Yet when asked what happens to current in a resistor when another parallel resistor was removed, you all incorrectly assumed that the current from the removed resistor still existed and now how to travel through the remaining ones.

The fact that you combine this unfounded and incorrect assumption about current remaining when the element through which it flows is gone with the [correct] way you predicted the current in parallel resistors [where the current through resistor 1 is calculated without any reference to resistors 2 s value or existence or the current that might or might not flow through resistor 2] in the same lab shows you are still not thinking analytically.

Let me put it numerically. I have resistor 1 of 40 ohms with 20 volts across it. A current of 0.5 amps flows through it. I now connect resistor 2 of 20 ohms in parallel with it. Resistor 2 sees the same 20 volts across it and produces a current of 1 amp, while resistor 1 produces the same 0.5 amps. I now disconnect resistor 2 and have resistor 1 in the exact same circumstance it originally was in. Now you are telling me that even though everything is the same as before, it will produce more than 0.5 amps and you would probably say 1.5 amps. I hope by now you realize this makes no sense.

You all should know that the voltage drop across an element [ bulb, resistor, etc.] causes the conduction electrons in that element to move. If you remove that element those electrons are no longer there, the current they provided is gone. The only reason removal of one parallel resistor would increase the current in the other remaining parallel resistors is if there is another resistance in series. In this case, the reduction in current due to the removal of the parallel resistance would reduce the current through the series resistance. This would reduce the voltage drop through the resistance in series, leaving more voltage drop available for the remaining parallel resistances causing an increase in their current. This increase is only very indirectly related to and certainly not equal to, the current that used to flow in the removed resistor.

Honors Assignment

Try to get some of this done tonight. The total assignment is due Thursday. A full schedule will be posted tomorrow, if all goes well.

Read Chap 10: Sect 1,2,3,4 and Notes on Fluid Dynamics pages 1 and do Chapt 10 question 3 (its tough and you’ll have to think) and prob 2, 5, 7,9,

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

Magnetics Notes

A student asked why there was no N/h in the equation for filed produced by a current in a solenoid. The equation uses the number of turns per meters of solenoid. This is exactly the same as taking the total number of turns and dividing by the height (or length if its horizontal) of the solenoid, i.e. turns per m = N/h

AP Geometric Optics Schedule

We will now study light's interaction with optical devices those that reflect or bend light to form images. We will continue at our rapid pace so pay attention and hang on. There are some enjoyable aspects to this topic, some illusions and magic tricks so we will have some fun, but we will move fast.

The problem sheet assignment for this unit is problems 13 through 18 on the problem sheet from Unit 14 A

Also note the break assignment. This assignment is key and will make up a large part of your grade for fourth quarter. We will have fewer than two full weeks together between my return and your exam, so be mature and bear down for the home stretch.

http://h1.ripway.com/DrCherdack/APUnit14BLightsched-11.doc

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

http://h1.ripway.com/DrCherdack/SummaryofGeoOpticsrev4-10.doc

AP Physical Optics Notes

Sarah Valente uncovered another error in my notes. I hope this is the last one. Here is the link again.

http://h1.ripway.com/DrCherdack/PhysicalOpticsSummary11.doc