Case study·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 turntable of moment of inertia rotates freely at . A piece of clay falls vertically and sticks at a distance from the axis. External torque about the axis is negligible.
Total: 5 marks
(a) Find the final moment of inertia. (1 mark)
(b) Find the final angular speed. (1 mark)
(c) Find the initial rotational kinetic energy. (1 mark)
(d) Find the final rotational kinetic energy. (1 mark)
(e) Explain why angular momentum is conserved but kinetic energy is not. (1 mark)
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