## Physics 2B Final Average

The average score on the final was 73.4%

The grading followed the cutoffs on the syllabus.

## Study Guide for the Final

Problems to focus on:

Chapter 26: 5, 20, 27, 30, 42, 51

Chapter 27:  1, 16 (and stationary observer variation), 20, 31, 36

Chapter 28: 8, 9, 13, 35, 40

Chapter 29: 40

Chapter 30: 5, 25

Notes: You may bring one side of an 8.5 x 11 sheet of paper with equations.  Don’t put examples on it.

Topics may include:

RMS current and voltage, power use, impedance, RLC circuits, relative motion, relativistic effects, length contraction, time dilation, the photoelectric effect, particle in a box, absorption and emission, binding energy, radioactive decay and half lives.

## Physics 2B Final

Wednesday May 30, 8:00 AM.

~ 2 hours

Chapters 26, 27, 28, 29, 30.  (Not all the material from 28, 29, 30 will be on the final)

## Test 5 Preparation

Know how to do these problems:

Chapter 24: 2, 14, 18, 25, 29, 31

Chapter 25: 8, 15 (try #16), 23, 28, 31, 37, 45

Other types of problems may show up on the test, but the list above will cover at least most (if not all) problems that will be on the test.

## No class Friday

Seems like there will be no class Friday.

Thanks

## Extra Credit + Next Week

You can get extra credit for five test problems that you missed points on (any test).

Five problems maximum.

Do the part of the problem that you missed originally.

You’ll get two points per problem or three points if you missed half or more of the points for the problem.  (You can even do things like missing factors of 10).

Also, if you would like to replace your lowest test score with the score from the final, the requirement will be that the class has a total of 50,000 points on Khan Academy for everyone to have the option.  Right now the class has 17,643 points.  I personally have 14,091 points, so that should be reasonable.  If the class doesn’t reach 50,000 points, you can still get the option if you personally reach 10,000 points.

I would suggest trying some of the math exercises on things like natural logarithms, exponents, and other things related to the class.  As well as viewing videos on topics we’re covering.

## Study Guide for Fourth Test

For the test next Tuesday, in preparation, focus on these problems:

Chapter 22: 9, 22, 33, 37, 51, 55

Chapter 23: 3, 19, 26, 38, 44, 61

Topics include  current, voltage, total charge that flows, resistivity, electric field and potential difference, power, circuit diagrams, resistors and circuits in series and parallel (including equivalent resistance and capacitance), current and voltage in circuits, RC circuits.

Even solutions: chapter 22:

22: 50 ohm meters

chapter 23:

26: 1 A & 5V.  5V & 0.5 A, 2.5 V & 0.5A, 2.5 V & 0.5 A

b) 2.24 x 10^-5 C

44: a) 1.8 x 10^-5 C, zero amps

b) 5.5 V, I = 0.11 A, Q = 1.1 x 10^-5 C

## Study Guide for Third Test

For the test next Tuesday, in preparation, focus on these problems:

Chapter 20: 1, 8, 25, 33, 38, 44, 58, 63

Chapter 21: 3, 8, 22, 34, 40, 73

Topics include electricity, conduction, capacitors, excess charge and ratios, dipoles, electric fields, comparison of energies and forces, electric potential, movement of charges.

For #73, the Iron atom is overall neutral.  The potential energy between the positive charges (proton and nucleus) will push them away from each other.  It’s as if the proton is rolling up a hill as it approaches the nucleus.  The problem asks for the situation necessary for the proton to just reach the edge of the nucleus.  The mathematics is the same as if the charge of the nucleus was concentrated at the very center of the nucleus.  It would take much more energy to actually enter the nucleus.

Let me know if you have questions.

## Study Guide for Second Test

Focus on these problems:

Chapter 18:

31, 41, 51, 60, 71

Chapter 19:

3, 4, 5, 9, 14, 25, 29, 30, 33

The topics may include:

converging and diverging lenses

myopia & hyperopia

reflection/refraction

images through lenses

cameras

telescope

resolution

prism

Since the chapters are related, there will be a bit more on chapter 19.  For a telescope/microscope problem I’ll provide the sign (+ & -) rules for a question on the test.  I will also provide constants – speed of light, etc.

Bring a note card with the equations.

Test next Monday.

## Notes on Ray Optics Homework Problems

Received a few questions about the homework, a few of them are challenging.  If the language of the book doesn’t make sense, ask me questions.  Generally I can decipher what they mean.  Problem #54 is probably the most complicated problem, you need to use a bit of trigonometry.  Draw a large diagram for that problem and it should be a little easier.

For #41, basically you need a more than one triangle and a few variables.  It uses geometry and algebra both.  As well as the law of reflection.  You might want to draw out the rays and then use parallel and perpendicular lines to create other triangles that might be useful.

51, the key phrase in the problem is that when you look at the target, the gaze is 30 degrees below horizontal.  I’ll draw a diagram of what that means tomorrow in class.

54, it’s asking for the angle labeled in the diagram theta 1 for ‘total internal reflection on the hypotenuse of the glass prism’.  So specifically against the edge that is the hypotenuse of the triangular prism.

60, there is a piece of glass on top of an amoeba, the thickness is given.  The light will refract when it enters the glass making it appear like the amoeba is in a different position.  It’s similar to the example I did in class with the air bubble in the middle of the submarine window.  You use a derived equation – equation 18.7.

71, use the magnification equation and thin lens equation.  It will be a converging lens since the image is real.  And it says the image will be smaller and upright (it doesn’t specifically say upright, but apparently it’s implied).