```選自 Principles of Physics (Halliday, Resnick and walker, 9th Edition)
Ch 16
10, 12, 19, 25, 58, 65, 71, 79
Ans
10) (a) 6.0 cm; (b) 1.0×102 cm; (c) 2.0 Hz; (d) 2.0×102 cm/s; (e) –x direction;
(f) 75 cm/s; (g) –2.0 cm.
12) 1.35π m/s
19) 121 m/s
58) (a) 0.846 kg; (b) The mass cannot set up a standing wave on the string.
65) (a) 2.0 mm; (b) 95 Hz; (c) + 30 m/s; (d) 31 cm; (e) 1.2 m/s
71) (a) 2.83 m/s; (b) 9.22 N; (c) 0; (d) 26.1 W; (e) 0; (f) 0; (g) ± 0.375 cm
79) (a) 148 m/s; (b) 3.00 m; (c) 1.50 m; (d) 49.3 Hz; (e) 98.7 Hz

1. A steel piano wire 50 cm long, of mass 5 g, is stretched with a tension of 400 N.
(a) What is the frequency of its fundamental mode of vibration?
(b) What is the highest overtone that could be heard by a person who is capable
of hearing frequency up to 10,000 Hz?
Ans. (a) 200 Hz, (b) 49 (50th harmonic)
2. A stretched string is observed to vibrate with a frequency of 30 Hz in its
fundamental mode when the supports are 60 cm apart. The amplitude at the
antinode is 3 cm. The string has a mass of 30 g.
(a) What is speed of propagation of a transverse wave in the string?
(b) Compute the tension in the string.
Ana. (a) 36.0 m/s, (b) 64.8 N
Ch 17
12, 26, 28, 35, 59, 66, 68
Ans
12) (a) 1.50 Pa; (b) 158 Hz; (c) 2.22 m; (d) 350 m/s.
26) (a) 0.080 W/m2; (b) 0.013 W/m2.
28) 1.26
35) (a) 7.37 × 10-5 W/m2; (b) 5.53 nW
59) (a) 1.023 kHz; (b) 1.047 kHz
66) (a) 598 Hz; (b) 608 Hz; (c) 589 Hz.
68) 3.25102 m/s

1. A window whose area is 1 m2 opens on a street where the street noises result in an
intensity level, at the window, of 50 db. How much “acoustic power” enters the
window via the sound waves?
Ans. 10-7 W
2. A railroad train is traveling at 30 m/s in still air. The frequency of the note emitted
by the locomotive whistle is 500 Hz. What is the wavelength of sound waves
(a) in front of and
(b) behind the locomotive?
What would be the frequency of the sound heard by a stationary listener
(c) in front of and
(d) behind the locomotive?
What would be heard by a passenger on a train traveling at 15 m/s and
(e) approaching the first.
(f) receding from the first
(g) How would each of the preceding answers be altered if a wind of speed 10
m/s were blowing in the same direction as that in which the locomotive was
traveling?
Ans. (a) 0.63 m, (b) 0.75 m, (c) 548 Hz, (d) 460 Hz, (e) 520 Hz, (f) 476 Hz.
(g) 0.65 m, 0.73 m, 547, 458, 569, 439 Hz
3. Two whistles A and B, each have a frequency of 500 Hz. A is stationary and B is
moving toward the right (away from A) at a speed of 50 m/s. An observer is
between the two whistles, moving toward the right with a speed of 25 m/s. Take
the speed of the sound in air as 350 m/s.
(a) What is the frequency from A as heard by the observer?
(b) What is the frequency from B as heard by the observer?
(c) What is the beat frequency heard by the observer?
Ans. (a) 464.3 Hz, (b) 468.8 Hz, (c) 4.5 Hz.
Ch 18
3, 36, 41, 47, 48, 50, 60
Ans
3) 348 K
36) (a) 22.7 kcal; (b) 1.11 kcal; (c) 960℃.
41) (a) 0°C; (b) 2.5°C
47) (a) 6.0 cal; (b) -43 cal; (c) 40 cal; (d) 18 cal; (e) 18 cal
48) –10.0 J
50) (a) +8.0 J; (b) 9.0 J.
60) (a) 16.5 °C; (b) We expect (and this is supported by the result in the next part) that
greater conductivity should mean a larger rate of conductive heat transfer; (c)
14.5 °C.

1. Consider the isothermal compression of 0.1 mol of an ideal gas at T  0o C . The
initial pressure is 1 atm and the final volume is 1/5 the initial volume.
(a) Determine the work required
(b) Does the gas exchange heat with its surrounding? If so, how much and in
which direction?
(c) What is the change in internal energy?
Ans. (a) 366 J, (b) Yes; 366 J out, (c) Zero.
2. An ideal gas initially at 10 atm and 300 K is permitted to expand adiabatically
until its volume is doubles. Find the final pressure and temperature if the gas is (a)
monatomic; (b) diatomic.
Ans. (a) 3.14 atm, 189 K, (b) 3.79 atm, 227 K.
3. During an adiabatic expansion, the temperature of 0.1 mol of oxygen drops from
30o C to 10o C. How much work does the gas do? How much heat is added?
Ans. 42.0 J, zero.
Ch 19
13, 19, 21, 25, 44, 56, 63, 67, 75, 83
Ans
13) (a) 1.5 mol; (b) 1.8 × 103 K; (c) 6.0 × 102 K; (d) 5.0 kJ
19) (a) 511 m/s; (b) -200°C; (c) 899°C
21) 1.8 × 102 m/s
25) (a) 5.65 × 10-21 J; (b) 7.72 × 10-21 J; (c) 3.40 kJ; (d) 4.65 kJ
44) (a) –5.0× 103 J; (b) 2.0× 103 J; (c) 5.0× 103 J.
56) (a) 2.46 atm; (b) 351 K; (c) 0.389 L.
63) (a) 3.74 kJ; (b) 3.74 kJ; (c) 0; (d) 0; (e) -1.81 kJ; (f) 1.81 kJ; (g) -3.22 kJ;
(h) -1.93 kJ; (i) -1.29 kJ; (j) 520 J; (k) 0; (1) 520 J; (m) 0.0246 m3; (n) 2.00 atm;
(o) 0.0373 m3; (p) 1.00 atm
67) (a) 2.00 atm; (b) 333 J; (c) 0.961 atm; (d) 236 J
75) (a) 900 cal; (b) 0; (c) 900 cal; (d) 450 cal; (e) 1200 cal; (f) 300 cal; (g) 900 cal;
(h) 450 cal; (i) 0; (j) -900 cal; (k) 900 cal; (l) 450 cal
83) (a) 8.0 atm; (b) 300 K; (c) 4.4 kJ; (d) 3.2 atm; (e) 120 K; (f) 2.9 kJ; (g) 4.6 atm;
(h) 170 K; (i) 3.4 kJ

1. A Carnot engine whose high-temperature reservoir is at 400 K takes in 100 cal of
heat at this temperature in each cycle, and gives up 80 cal to the low-temperature
reservoir.
(a) What is the temperature of the later reservoir?
(b) What is the thermal efficiency of the cycle?
Ans. (a) 320 K. (b) 20%.
2. A carnot engine is operated between two heat reservoirs of 400 K and 300 K.
(a) If the engine receives 1200 cal from the reservoir at 400 K in each cycle, how
many calories per cycle does it reject to the reservoir at 300 K?
(b) If the engine is operated in reverse, as a refrigerator and receives 1200 cal
from the reservoir at 300 K, how many calories does it deliver to the reservoir
at 400 K?
(c) How many calories would be produced if the mechanical work required to
operate the refrigerator in part (b) were converted directly to heat?
Ans. (a) 900 cal, (b) 1600 cal, (c) 400 cal.
Ch 20
14, 17, 29, 33, 35, 52, 62
Ans
14) (a) 3.00; (b) 6.00; (c) 0; (d) 21.6 J/K; (e) 0.
17) (a) 0.333; (b) 0.215; (c) 0.644; (d) 1.10; (e) 1.10; (f) 0; (g) 1.10; (h) 0; (i) -0.889;
(j) -0.889; (k) -1.10; (l) -0.889; (m) 0; (n) 0.889; (o) 0
29) (a) 2.27 kJ; (b) 14.8 kJ; (c) 15.4%; (d) 75.0%; (e) greater
33) (a) 1.47 kJ; (b) 554 J; (c) 918 J; (d) 62.4%
35) (a) 3.00; (b) 1.98; (c) 0.660; (d) 0.495; (e) 0.165; (f) 34.0%
52) (a) 7.2  103 J; (b) 9.6  102 J; (c) 13%.
62) (a) 700 J; (b) 0; (c) 50 J; (d) 700 J; (e) 0.254 m3; (f) 0.284 m3; (g) 0; (h) –625 J;
(i) 0; (j) 625 J.

1. Heat is added to 0.5 kg of ice at 0o C until it is all melted. (specific heat of ice is
c = 0.5 3calg-1K-1= 2.3 J g-1K-1, latent heat of fusion of ice is
L  3.33 105 J/kg )
(a) What is the change in entropy of the water?
(b) If the source of heat is a very massive body at a temperature of 20o C, what is
the change in entropy of the body?
(c) What is the total change in entropy of the water and the heat source?
Ans. (a) 610 J/K, (b) -568 J/K, (c) 41.6 J/K.
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