Physics & Astronomy

Physics 123 Announcements

Serious typo on 32-1(a) of the homework:
Replace the entire HINT with: Please refer to Table 44.2. Be aware that the table includes the mass of the electrons in orbit around the nucleus. Note that in Eq. (44.2), the electron masses cancel automatically between ZM(H) and M(X).

There are some typos in problems 29-3 and 29-5 of the homework:
Both problems should start from Eq. (40.6) instead of (40.3).
For problem 29-3, you are deriving Eq. (40.2) instead of (40.1).
For problem 29-5, you are deriving Eq. (40.1) instead of (20.18).
Sorry for the inconvenience.

Students pointed out that Lab #8 wasn't due until today, yet it got highlighted in Exam 3, which ended yesterday. Some students felt disadvantaged, although there were a number of students who got it right without doing the lab first. I decided that anyone who missed points on problem 4 of exam 3 may correct their test (use a different colored pen to mark in your corrections) and resubmit your exam in the homework boxes by Wednesday. You are on your honor not to consult the posted solution before resubmitting your test. If you resubmit your exam 3, you can get back half your points missed on problem 4, if you do the problem correctly.

Practice Exam I
Answers:
1. 30 liters
2. 40,000 Pa
3. (a) 30.0 m/s (b) 20
4. (a) 1.219 (b) 1.221
5.
6. 1s
7.
8. 8.9m
9. 85Hz
10. 7900 kg/m^3
Quiz Questions

Practice Exam II
Answers:
1. (b) -32F
2. (a) 0.342m (b) 1.0L
3. (a) 2.4x10^22 (b) 3.0x10^22
4. 4.5hr
5. (a) 2.0x10^4 J (b) 2.0x10^4 J
6. (a) 764 m/s (b) 1.30 m
7. (b) 152J (c) 760J (d) 912J
8. 1.40 L
9. 1.32
10. (a) 0.33 (b) 400K
11. (a) 95J (b) 0.95 J/K
Quiz Questions

Practice Exam III
Answers:
1.
2. any angle 0-90degrees
3. Maximum intensity is I/8 when polarizer is at 45 degrees
4. (a) 40cm (b) 36cm
5. (a) 43cm (b) 43cm
6. 25.0cm
7. (a) 60cm, -5 (b) 25cm
8. (a) 500microns (b) I(peak)=4I(one beam)
9. theta=5.7 degrees
10. 115nm
11. 100microns
12. (a) 0.0038ly (b) 3microns
Quiz Questions

Practice Exam IV
Answers:
1. (a) –0.976c (b) 1.9x10^42 J
2. (a) 657 nm (b) -0.6c
3. 0.998c
4. (a) T=5800 K (b) 19 ly
5. (a) 271 nm (b) 0.7 fm
6. (a) 1280 nm (b) 2.78
7. (a) 0.208 MeV (b) 52 degrees
8. (a) 8.9x10^8 y (b) 341.4MeV and 343.7 MeV (c) 0.49 MeV
9. (a) 105 MeV (b) 0.156 MeV
Quiz Questions