FRQ — Physical World and Measurements

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 viscous drag force on a small sphere depends on coefficient of viscosity

\eta

, radius

r

, and speed

v

. Use dimensional analysis to find the proportional form of

F

Total: 5 marks

(a) Assume $F\propto \eta^a r^b v^c$ and write dimensions. (1 mark)

(b) Find $a$ , $b$ , and $c$ . (3 marks)

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

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