FRQ — Thermodynamics

Long answer·Hard exam skill (4/5)·No calculator

Difficulty guide

The label describes the problem, not your ability.

1/5 - Foundational

Warm-up setup; checks one basic idea.

2/5 - Routine exam skill

Normal syllabus skill; usually one main rule or interpretation.

3/5 - Standard multi-step

Exam-style problem with multiple steps or a common trap.

4/5 - Hard exam skill

High-end exam problem; combines methods carefully.

5/5 - Challenge

Stretch problem beyond normal exam pressure.

Question

A gas goes around a rectangular cycle A-B-C-D-A on a

P

V

diagram. The lower pressure is

1.0\times10^5\text{ Pa}

, upper pressure is

4.0\times10^5\text{ Pa}

, lower volume is

2.0\times10^{-3}\text{ m}^3

, and upper volume is

5.0\times10^{-3}\text{ m}^3

. The direction is A to B to C to D to A as shown.

Total: 4 marks

(a) Find the magnitude of net work in one cycle. (2 marks)

(b) State whether the sign of work done by the gas is positive or negative for the shown direction. (1 mark)

Your response (optional — you can also work on paper)

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