Download Exam 5 Physics 124A Fall 2003 Name:

Exam 5 Physics 124A Spring 2006
Name:
Time Allowed: 2 hours
Each question is worth 5 points.
Credits are given for numerical problems only if evidence of calculations is presented.
1. Helium gas becomes liquid at the temperature of -452 Fº. What is the temperature in K?
(A) 77 K
(B) 15 K
(C) 4 K
(D) -16 K
2. Which of the following statements concerning heat is incorrect?
(A)
(B)
(C)
(D)
the unit of heat is J
the unit of heat is calorie
heat is stored energy
heat flows from high temperature to low temperature
3. A 4.00-kg metal object requires 8.00  103 J of heat to raise its temperature from 10.0 °C to 30.0 °C.
What is the specific heat capacity of the metal?
(A)
(B)
(C)
(D)
100 J/(kg  C°)
200 J/(kg  C°)
300 J/(kg  C°)
400 J/(kg  C°)
4. Heat is absorbed at the same rate by a copper and an aluminum sample of equal mass and equal initial
temperature. Aluminum has the higher specific heat capacity. Which of the following statements is correct?
(A) After 5 seconds, aluminum has the higher temperature.
(B) After 5 seconds, copper has the higher temperature.
(C) After 5 seconds, both have the same temperature.
(D) It takes a longer time for copper to increase its temperature by the same amount as aluminum.
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5. An aluminum sample of mass 10 g at 100ºC is dropped into a fully insulated container containing 4 g of
water, initially at 20ºC. Determine the final temperature of the mixture.(The specific heats of water and
aluminum are 1.0 cal/g/Cº and 0.2 cal/g/Cº respectively)
(A) 72 ºC
(B) 65 ºC
(C) 47 ºC
(D) 39 ºC
6. Which of the following quantities for the water substance is most relevant for the occurrence of steam
scorching?
(A) latent heat of fusion
(B) latent heat of vaporization
(C) specific heat capacity
(D) boiling point
7. Which of the following statements is true when 60 kg of water initially at 20ºC is completely frozen to
become ice at 0ºC? (The latent heat of fusion of water is 33.5×104 J/kg. The specific heat of water is 4186
J/kg/Cº)
(A) 8.4×106 J of energy is released
(B) 8.4×106 J of energy is absorbed
(C) 2.52×107 J of energy is released
(D) 2.52×107 J of energy is absorbed
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8. Find the number of molecules in 1.0 L of water. (1L=10-3m3. The molecular formula of water is H2O, the
atomic masses of H and O are 1 and 16 respectively, and Avogadro’s number is 6.0×1023)
(A) 5.8×1024
(B) 3.3×1025
(C) 7.2×1026
(D) 4.6×1027
9. Find the volume occupied by 8 moles of oxygen at 150ºC and a pressure of 20 ATM, assuming that the
gas behaves as an ideal gas.(1 ATM=105 Pa, R=8.31J/K/mole)
(A) 0.042 m-3
(B) 0.037 m-3
(C) 0.014 m-3
(D) 0.005 m-3
10. An ideal gas in a steel vessel initially at 10ºC and atmospheric pressure is heated to 80ºC. Find its
pressure.
(A) 8.00 ATM
(B) 4.00 ATM
(C) 2.50 ATM
(D) 1.25 ATM
11. In a jar containing a mixture of the monatomic gases helium and neon, the ratio of the rms velocity of the
neon atoms to that of the helium atoms is (The atomic masses of helium and neon are 4 and 20
respectively)
(A) 5.0
(B) 2.5
(C) 0.45
(D) 0.20
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12 When the gas enclosed beneath the piston shown in the figure receives 650 J of heat, Q, from its
surroundings, its internal energy decreases by 320 J. How much work is performed by the gas in raising
the piston.
(A)
(B)
(C)
(D)
-530 J
530 J
–770 J
770 J
13. A fixed amount of ideal gas is compressed isothermally. Which entry in the table below correctly depicts
the sign of the work done W by the gas, the change in the internal energy U , and the heat absorbed Q from
with the environment?
A)
B)
C)
D)
W
+
+
U
0
0
0
Q
0
+
-
14. During a change of states, an ideal gas absorbs 200J of heat and performs an equal amount of work. What
kind of process is this?
(A) adiabatic
(B) isobaric
(C) isochoric
(D) isothermal
15. During an adiabatic expansion, 8 moles of an ideal monatomic gas initially at 70ºC performs 6000J of work.
What is its final temperature?
(A) 40ºC
(B) 30ºC
(C) 20ºC
(D) 10ºC
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Use the following to answer questions 16 and 18:
An ideal monatomic gas expands isobarically from state A to state B. It is then compressed isothermally from
state B to state C and finally cooled at constant volume until it returns to its initial state A.
VA = VC = 2  10–3 m3
VB = 8  10–3 m3
PA = PB = 1  106 Pa
TA = 300 K
16. What is the pressure of the gas when it is in state C?
(A)
(B)
(C)
(D)
2 ATM
4 ATM
20 ATM
40 ATM
17. How much work is done by the gas in expanding isobarically from A to B?
(A)
(B)
(C)
(D)
8  103 J
6  103 J
4  103 J
2  103 J
18. How much work is done by the gas when its state changes from C to A?
Ans:
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19. A longitudinal wave with a frequency of 3.0Hz takes 0.5 s to travel the length of a 2 m slinky. Determine
the wavelength of the wave.
A)
B)
C)
D)
0.5 m
0.7 m
1.0 m
1.3 m
20. Two foam cups floating in ocean water 1.5m apart are observed to oscillate 180° out of phase with the same
period of 0.2s when a surface wave passes by. What is the largest possible value for the velocity of the
wave?
(A) 7.5 m/s
(B) 10 m/s
(C) 15 m/s
(D) depends on the nature of the wave
21. The diagram shows the various positions of a child in motion on a swing. Somewhere in front of the child a
stationary whistle is blowing.
At which position(s) will the child hear the lowest frequency for the sound from the whistle?
(A) at both A and D
(B) at C when moving toward B at
(C) B when moving toward A
(D) at C when moving toward D
22. The frequency of a whistle on a train is 770Hz when it is stationary. What is the frequency heard when it is
moving toward an observer with speed 33m/s? (The speed of sound is 330m/s)
A)
B)
C)
D)
856Hz
821Hz
765Hz
700Hz
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