Sample Multiple Choice Questions from past AP Physics B tests –
Atomic, Molecular, Thermal
1984 B multiple choice
30. A 2-kilogram block of metal with a specific heat of 100 joules per kilogram*Kelvin falls from rest through a
distance of 100 meters to the Earth's surface. If half of the potential energy lost by the fallen block is converted
to internal energy of the block, the temperature change of the block is most nearly
(A) 1 K
(B) 5 K
(C) 10 K
(D) 25 K
(E) 45 K
31. The maximum efficiency of a heat engine that operates between temperatures of 1500 K in the firing chamber
and 600 K in the exhaust chamber is most nearly (A) 33% (B) 40% (C) 60% ( D) 67% (E) 100%
32. An ideal gas is made up of N diatomic molecules, each of mass M. All of the following statements about this gas
are true EXCEPT:
(A) The temperature of the gas is proportional to the average translational kinetic energy of the molecules.
(B) All of the molecules have the same speed.
(C) The molecules make elastic collisions with the walls of the container.
(D) The molecules make elastic collisions with each other.
(E) The average number of collisions per unit time that the molecules make with the walls of the container
depends on the temperature of the gas.
A thermodynamic system is taken from an initial state X along the path XYZX as shown in the PV-diagram above.
33. For the process XY, U is greater than zero and
(A) Q<0 and W = 0
(B) Q<0 and W>0
(C) Q>0 and W<0
(D) Q>0 and W=0
34. For the process YZ, Q is greater than zero and
(A) W<0 and U=0 (B) W=0 and U<0 (C) W=0 and U>0
( D) W >0 and U=0 (E) W>0 and U>0
(E) Q>0 and W>0
50. An ideal gas confined in a box initially has pressure p. If the absolute temperature of the gas is doubled and the
volume of the box is quadrupled, the pressure is (A) p/8 (B) p/4 (C) p/2 (D) p (E) 2p
68. Heat is added at a constant rate to a sample of pure substance that is initially a solid at temperature T o. The
temperature of the sample as a function of time is shown in the graph above. From the graph, one can conclude
that the
(A) substance sublimes directly from the solid phase to the vapor phase
(B) melting point is T2
(C) specific heat is greater for the liquid phase than for the solid phase
(D) heat of fusion and heat of vaporization are equal
(E) specific heat of the solid increases linearly with temperature
1988 MCB
23. An ideal gas in a closed container initially has volume V, pressure P. and Kelvin temperature T. If the
temperature is changed to 3T, which of the following pairs of pressure and volume values is possible?
(A) 3P and V (B) P and V
(C) P and V/3 (D) P/3 and V
(E) 3P and 3V
24. If three identical samples of an ideal gas are taken from initial state I to final state F along the paths IAF, IF, and
IBF as shown in the pV-diagram above, which of the following must be true?
(A) The work done by the gas is the same for all three paths.
(B) The heat absorbed by the gas is the same for all three paths.
(C) The change in internal energy of the gas is the same for all three paths.
(D) The expansion along path IF is adiabatic.
(E) The expansion along path IF is isothermal.
25. If the average kinetic energy of the molecules in an ideal gas at a temperature of 300 K is E, the average kinetic
energy at a temperature of 600 K is
(A)
E
2
(B) E
(C)
2E
(D) 2E
(E) 4E
26. A metal rod of length L and cross-sectional area A connects two thermal reservoirs of temperatures T1 and T2.
The amount of heat transferred through the rod per unit time is directly proportional to
(A) A and L
(B) A and 1/L
(C) 1/A and L
(D) 1/A and 1/L
(E)
A and L2
48. Which of the following is always a characteristic an adiabatic process?
(A) The temperature does not change (T = 0).
(B) The pressure does not change ( P = 0).
(C) The internal energy does not change (U = 0).
(D) No heat flows into or out of the system (Q = 0)
(E) No work is done on or by the system (W = 0)
An ideal gas undergoes a cyclic process as shown on the graph above of pressure rho versus volume V.
49. During which process is no work done on or by the gas?
(A) AB
(B) BC
(C) CD
(D) DE
(E) EA
50. At which point is the gas at its highest temperature?
(A) A
(B) B
(C) C
(D) D
(E) E
70. Gas in a chamber passes through the cycle ABCA as shown in the diagram above. In the process AB, 12 joules
of heat is added to the gas. In the process BC, no heat is exchanged with the gas. For the complete cycle
ABCA, the work done by the gas is 8 joules. How much heat is added to or removed from the gas during
process CA ?
(A) 20 J is removed.
(B) 4 J is removed.
(C) 4 J is added.
(D) 20 J is added.
(E) No heat is added to or removed from the gas.
1993 MC-B
23. If the gas in a container absorbs 275 joules of heat, has 125 joules of work done on it, and then does 50 joules of
work, what is the increase in the internal energy of the gas?
(A) l00 J
(B) 200 J (C) 350 J
(D) 400 J
(E) 450 J
Questions 24-25
A piece of metal with a mass of 1.50 kilograms, specific heat of 200 J/kg · C°, and initial temperature of 100° C is
dropped into an insulated jar that contains liquid with a mass of 3.00 kilograms, specific heat of l,000 J/kg · C°, and
initial temperature of 0° C. The piece of metal is removed after 5 seconds, at which time its temperature is 20° C.
Neglect any effects of heat transfer to the air or to the insulated jar.
24. The temperature of the liquid after the metal is removed is
(A) 0° C
(B) 4°C (C) 8° C (D) 10° C
(E) 20° C
25. The average rate at which heat is transferred while the piece of metal is in the liquid is
(A) 4,000 J/s (B) 4,800 J/s (C) 6,000 J/s (D) 9,600 J/s
(E) 16,000 J/s
54. Atoms of isotopes of the same element contain the same number of
(A) protons but a different number of neutrons (B) electrons but a different number of protons
(C) neutrons but a different number of protons (D) neutrons as electrons (E) protons as neutrons
55. In each cycle of a certain Carnot engine, 100 joules of heat is absorbed from the high-temperature reservoir and
60 joules is exhausted to the low-temperature reservoir. What is the efficiency of the engine?
(A) 40%
(B) 60%
(C) 67%
(D) 150%
(E) 167%
Questions 22-23
A certain quantity of an ideal gas initially at temperature T, pressure p0, and volume V0 is compressed to one-half its
initial volume. As shown above, the process may be adiabatic (process 1), isothermal (process 2), or isobaric
(process 3).
22. Which of the following is true of the mechanical work done on the gas?
a. It is greatest for process 1.
b. It is greatest for process 3.
c. It is the same for processes I and 2 and less for process 3.
d. It is the same for processes 2 and 3 and less for process 1.
e. It is the same for all three processes.
23. Which of the following is true of the final temperature of this gas?
a. It is greatest for process 1.
b. It is greatest for process 2.
c. It is greatest for process 3.
d. It is the same for processes 1 and 2.
e. It is the same for processes 1 and 3.
24. In a certain process, 400 J of heat is added to a system and the system simultaneously does 100 J of work. The
change in internal energy of the system is
a. 500 J
b. 400 J
c. 300 J
d. -100 J
e. -300 J
25. An ice cube of mass m and specific heat ci is initially at temperature T1, where T1 < 273 K. If L is the latent
heat of fusion of water, and the specific heat of water is cw, how much energy is required to convert the ice cube
to water at temperature T2, where 273 K < T2 < 373 K?
a. m[ci (273 - T1) + L + cw (373 - T2)]
b. m[ci (273 - T1) + L + cw (T2 - 273)]
c. ci (273 - T1) + cw (T2 - 273)
d. mL + cw (T2 - T1 )
e. mL + (cw + ci)( T2 - T1)
52. An ideal gas is initially in a state that corresponds to point 1 on the graph above, where it has pressure p1,
volume V1, and temperature T1. The gas undergoes an isothermal process represented by the curve shown,
which takes it to a final state 3 at temperature T3. If T2 and T4 are the temperatures the gas would have at points
2 and 4, respectively, which of the following relationships is true?
a. T1 < T3
b. T1 < T2
c. T1 < T4
d. T1 = T2
e. T1 = T4
53. The absolute temperature of a sample of monatomic ideal gas is doubled at constant volume. What effect, if
any, does this have on the pressure and density of the sample of gas?
Pressure
Density
a. Remains the same
Remains the same
b. Remains the same
Doubles
c. Doubles
Remains the same
d. Doubles
Is multiplied by a factor of 4
e. Is multiplied by a factor of 4
Doubles
54. The disk-shaped head of a pin is 1.0 mm in diameter. Which of the following is the best estimate of the number
of atoms in the layer of atoms on the top surface of the pinhead?
a. 104
b. 1014
c. 1024
d. 1034
e. 1050
61. Which of the following statements is NOT a correct assumption of the classical model of an ideal gas?
a. The molecules are in random motion.
b. The volume of the molecules is negligible compared with the volume occupied by the gas.
c. The molecules obey Newton's laws of motion.
d. The collisions between molecules are inelastic.
e. The only appreciable forces on the molecules are those that occur during collisions.
62. A sample of an ideal gas is in a tank of constant volume. The sample absorbs heat energy so that its temperature
changes from 300 K to 600 K. If v1 is the average speed of the gas molecules before the absorption of heat and
v2 is their average speed after the absorption of heat, what is the ratio v2/ v1 ?
a. 1/2
b. 1
c.
2
d. 2
e. 4