Exam-style question
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If a solid disc is spun up from rest to a constant angular speed, what happens to its rotational kinetic energy?.
- A.It remains zero.
- B.It becomes negative.
- C.It increases.
- D.It decreases.
Model answer
What a good answer should say
- It increases.
Explanation
Why this works
Rotational kinetic energy is given by ½Iω²; starting from ω=0 and ending at ω>0, the energy increases, consistent with energy conservation as work is done on the disc.
Common mistake
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