Physics 122, Fall Quarter:
This page is reverse chronological order.
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Answers to hour test 2, 67.7 +/- 19.5 of 105

1.a. dW = 4 atmos (3-1 l) + 1 atmos (5-3 l) = 10 atmos-liter = 1000 J
1.b.  dW = (4-2 atmos)(2-1 l) = 2 atmos-liter = 200 J
1.c. eta = Wnet/Qin = 200/800 = 25%
1.d. Qout = Qin - Wnet = 800 - 200 = 600 J

2.a.  dQ=0 process, adiabatic compression in auto IC engine, do compress
it quickly, so no (little) heat escapes.
2.b.  dQ=0, dW = - dU, -10 = - dU, dU = + 10 J
2.c.  isometric, dVol = 0, dW = 0 = P dV
2.d.  dQ = dW + dU, energy is conserved

3.a.  k = dF/dX= (0.1 kg)(10)/0.4 m = 2.5 N/m
3.b.  T = 12 s/10 oscil = 1.2 s/oscil, f=1/T = 0.08 Hz, w = 2pif = 5 rad/s
3.c.  w = sqrt (k/m) = sqrt (2.5/0.1) = 5 rad/s, f = w/2 pi = 0.8 Hz,
T=1/f = 1.2 s
3.d.  vmax = w xmas = 5 x 0.1 = 0.5 m/s

4.a.  lamda1 = 2L = 2 m, l2 = L = 1 m, l3 = 2/3 L = 0.67 m
4.b.  T = mu (lamda.f)^2 = (0.04)(2 x 440)^2 = 30,000 N
4.c.  fret in the middle, L to L/2, doubles f to 880 Hz

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Answers to Hour Test #1.

1a)  PU = P(v/VU) = (1 atmos)(1/0.1) = 10 atmos
1b)  v(he)/v(O2) = sq rt (m(O2)/m(He) = sq rt (32/4) = 2.8
1c)  temperature measures the intensity of heat per atom, such as its kinetic energy, or per
unit mass (shaking solids).  ok hot and cold will do,  or KE = 3/2 kT will do.
Heat is the amount of thermal (motion) energy per object, the iron hammer had a heat of
100,000 J with respect to 10 degrees C, etc.

2.  P=rho g H = (1000)(10)(2)(100) = 2 M Pascals
F = P A = 2 M Pa x 0.01 m2 = 2 x 10^4 N

3.  Bforce = rho g Vol. = 1000 x 10 x 0.05 = 500 N
NET FORCE = 500 N - mg = 500 - 0.1 x 10 = 499 N

4.a) only.  vU/v = A/AU = 1/0.9 = 1.1,  10% increase in velocity

5a)  n = PV/RT,    P 10 = 14.7 psi = 25 psi = 1.7 x 10^5 Pa, R = 8.3, T=300K, V=0.05 m3, gives
n = 3.3 moles
b) N = Na x n = 2 x 10^24 molecules

6.  Qgain:  500(80+4.2) + 500(4.2)(Tf - 0)
Qloss:  400(4.2)(100 - Tf),  setting equal gives 0 degrees C.
not Q loss is initial minus final to be positive.  DH prefers this method since it keeps track
of the latent heats in better (for me) way.

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Ch 11:  

4.	6.7 x 10^6 J
14.	58 C
36.	4.9 x 10^4 J
20.	0.18 C
25.	687 J/kg C
43.	water, 92 s, alochol, 28 s
61.	4.5 x 10^6 J
78.	411 C
80.	88.7 C