Exam-style question
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A wheel of radius 0.5 m has a mass of 10 kg and is rotating at 20 rad s⁻¹. Which of the following expressions correctly gives its moment of inertia if it is approximated as a solid disc?.
- A.I = 0.5 kg m²
- B.I = 2.5 kg m²
- C.I = 5 kg m²
- D.I = 10 kg m²
Model answer
What a good answer should say
- I = 2.5 kg m²
Explanation
Why this works
For a solid disc, I = ½ M R². Substituting M = 10 kg and R = 0.5 m gives I = 0.5 × 10 × 0.25 = 2.5 kg m².
This value is used to relate torque and angular acceleration for the wheel.
Common mistake
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