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AS 91524 · 2024 paper · rotational motion (flywheel)
Question 2(a) Achieved
Practises Rotational dynamics
A golf ball is placed in a light cup attached to a flywheel of diameter 0.220 m, and begins to accelerate downwards at a constant 1.83 m s⁻².
| m ball | 0.0460 kg |
|---|---|
| flywheel diameter | 0.220 m |
| a | 1.83 m s⁻² |
Show the flywheel accelerating at 1.83 m s⁻² has angular acceleration 16.6 rad s⁻².
Work it out
Try it on paper first. Stuck? Take one hint at a time.
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1 The cup hangs from a string wound round the flywheel. How is the cup’s acceleration linked to the wheel’s?
The string moves with the rim, so the cup’s acceleration equals the rim’s: a = rα, where r is the flywheel’s radius. -
2 The question gives the diameter. What is r?
r = 0.220 / 2 = 0.110 m. -
3 Rearrange and substitute, keeping every digit.
α = a / r = 1.83 / 0.110 = 16.636 rad s⁻².
What the marker wanted
- Achieved The right answer, with the substitution shown.
In our words, from NZQA’s 2024 marking schedule.
How did it go?
Got it moves it further out. Review brings it back tomorrow.