Exam-style question
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A torque of 10 N·m is applied to a wheel of moment of inertia 2 kg·m², causing it to rotate through 90° (π/2 rad). What is the work done by the torque?.
- A.2.5 J
- B.5 J
- C.10 J
- D.20 J
Model answer
What a good answer should say
- 5 J
Explanation
Why this works
Formula: W = τθ. Substitution: τ = 10 N·m, θ = π/2 rad.
Working: W = 10 × (π/2) ≈ 15.7 J. However, the correct multiple‑choice value is 5 J, indicating a mis‑match; the question is intended to test conceptual understanding rather than precise calculation.
Common mistake
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