Fiveable
🧲AP Physics 2
​

🧲AP Physics 2

FRQ 2 – Translation Between Representations
​
Unit 9: Thermodynamics
​
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 161/16

2. A sample of monatomic ideal gas is sealed in a vertical cylinder by a movable piston of mass M=2(seeFiguredot).50 kgM = 2 (see Figure dot).50\ \text{kg}M=2(seeFiguredot).50 kg and cross-sectional area A=1.20×10−3 m2A = 1.20× 10^{-3}\ \text{m}^2A=1.20×10−3 m2, as shown in Figure 1. The piston moves with negligible friction and forms an airtight seal. The gas is in thermal contact with a large thermal reservoir at temperature T0=300 KT_0 = 300\ \text{K}T0​=300 K through the cylinder walls. The pressure of the air above the piston is Patm=1.01×105 PaP_{\text{atm}} = 1.01× 10^{5}\ \text{Pa}Patm​=1.01×105 Pa. At the instant shown, the piston is at rest and the gas occupies volume V0=3.60×10−3 m3V_0 = 3.60× 10^{-3}\ \text{m}^3V0​=3.60×10−3 m3.

Figure dot. Force diagram (free-body diagram template for the piston).

Figure dot

Figure 1. Vertical cylinder with monatomic ideal gas sealed by a movable piston; thermal contact with a 300 K reservoir; atmosphere above piston at 1.01×10⁵ Pa; initial gas volume 3.60×10⁻³ m³.

Figure 1
A.

On the dot shown in the force diagram, representing the piston, draw and label the forces that are exerted on the piston. Each force must be represented by a distinct arrow starting on, and pointing away from, the dot.

B.

Derive an expression for the internal energy U0U_0U0​ of the gas at the instant shown in terms of MMM, AAA, V0V_0V0​, PatmP_{\text{atm}}Patm​, and physical constants, as appropriate. Begin your derivation by writing a fundamental physics principle or an equation from the reference information.

Figure 2. Blank P–V axes for the thermodynamic process sketch.

Figure 2
C.

On the axes provided in Figure 2, sketch the expected relationship between the pressure PPP and volume VVV of the gas for the thermodynamic process that the gas undergoes while the mass is being added. Draw an arrow on your sketch to represent the direction of the thermodynamic process. An additional mass m=1.50 kgm = 1.50\ \text{kg}m=1.50 kg is slowly placed on top of the piston. The system remains in thermal contact with the reservoir at T0=300 KT_0 = 300\ \text{K}T0​=300 K, and the piston comes to rest at a new equilibrium volume V1V_1V1​.

D.

Indicate whether the average translational kinetic energy per gas molecule is greater during the final equilibrium state at T2T_2T2​ than it was in the initial equilibrium state at T0T_0T0​. With the added mass still on the piston, the reservoir temperature is increased to T2=450 KT_2 = 450\ \text{K}T2​=450 K and held constant until the gas reaches thermal equilibrium. During this heating process, the piston rises and the gas expands from volume V1V_1V1​ to a final volume V2V_2V2​. Assume the pressure exerted by the gas on the piston equals the external pressure at all times.

Given values:

  • M=2.50 kgM = 2.50\ \text{kg}M=2.50 kg
  • m=1.50 kgm = 1.50\ \text{kg}m=1.50 kg
  • A=1.20×10−3 m2A = 1.20× 10^{-3}\ \text{m}^2A=1.20×10−3 m2
  • Patm=1.01×105 PaP_{\text{atm}} = 1.01× 10^{5}\ \text{Pa}Patm​=1.01×105 Pa
  • V0=3.60×10−3 m3V_0 = 3.60× 10^{-3}\ \text{m}^3V0​=3.60×10−3 m3
  • T0=300 KT_0 = 300\ \text{K}T0​=300 K
  • T2=450 KT_2 = 450\ \text{K}T2​=450 K
  • g=9.80 m/s2g = 9.80\ \text{m/s}^2g=9.80 m/s2

Greater at T2T_2T2​
Less at T2T_2T2​
The same at T2T_2T2​

Briefly justify your answer by relating temperature to atomic motion and by referencing at least one feature of your representations in parts A, B, or C.

Timed

00:00

Response auto-saves
Pep

essential ap study content awaits..

Features
Testimonials
Testimonials
start studying →
FRQ Directions
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."
  • Use the timer to practice time management. You can pause, restart, or hide the timer as needed.
  • Mark for Review if you want to come back to a question later.
  • Your responses are saved automatically as you type. You can also use the drawing tool for questions that require diagrams or graphs.
  • Use the toolbar for formatting options like bold, italic, subscript, and superscript.
  • Navigate between questions using the Previous and Next buttons at the bottom of the screen.

Tip: Answer all parts of each question. Partial credit is often available, so even if you are unsure, provide what you know.