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🧲AP Physics 2
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🧲AP Physics 2

FRQ 4 – Qualitative/Quantitative Translation
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Unit 9: Thermodynamics
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FRQ Types & Units

Each FRQ type tests specific skills taught in particular units. Here's why certain units appear for each question type:

This mapping reflects College Board's exam structure - each FRQ type tests specific skills that are taught in particular units.

Practice FRQ 1 of 201/20

4. A sealed cylinder with a frictionless, massless piston contains n=0.50 moln=0.50\ \text{mol}n=0.50 mol of a monatomic ideal gas. Initially the gas is at pressure P1=1.0×105 PaP_1=1.0\times10^5\ \text{Pa}P1​=1.0×105 Pa and volume V1=1.0×10−2 m3V_1=1.0\times10^{-2}\ \text{m}^3V1​=1.0×10−2 m3. The cylinder is placed in thermal contact with a large reservoir, and the gas is taken from state 1 to state 2 by slowly adding small masses to the piston so that the pressure of the gas increases while the volume decreases, as shown in Figure 1. Throughout the process, the piston moves slowly enough that the gas is always approximately in thermal equilibrium. The reservoir temperature remains constant.

Figure 1. Sealed cylinder with frictionless, massless piston; monatomic ideal gas slowly compressed while in thermal contact with a constant-temperature reservoir.

Figure 1
A.

During the slow compression from state 1 to state 2, a student claims that the temperature of the gas must increase because the pressure increases.

Indicate whether the student's claim is correct or incorrect. Without manipulating equations, justify your answer by describing the temperature of the gas in terms of the motion of the gas atoms and by describing what it means for the gas to be in thermal contact with a reservoir at constant temperature.

B.

Derive an expression for the final volume V2V_2V2​ in terms of P1P_1P1​, V1V_1V1​, and P2P_2P2​ for the process described, assuming the gas remains at the reservoir temperature. Begin your derivation by writing a fundamental physics principle or an equation from the reference information. Express your answer using only P1P_1P1​, V1V_1V1​, and P2P_2P2​ (and constants, as appropriate).

C.

Indicate whether the expression you derived in part B is or is not consistent with your answer from part A. Briefly justify your answer by referencing how the result in part B depends on temperature and by describing the pressure the gas exerts on the container in terms of atomic collisions.

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Free Response Question Practice

This practice environment simulates the AP AP Physics 2 Free Response Questions section. Here are some guidelines:

  • Read each question carefullybefore responding. Pay attention to command verbs like "identify," "explain," "analyze," or "evaluate."
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Tip: Answer all parts of each question. Partial credit is often available, so even if you are unsure, provide what you know.