Exam-style question
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Which equation would you use to find the angular acceleration of a solid disc if a force of 10 N is applied at a radius of 0.2 m and the disc’s moment of inertia is 0.05 kg·m²?.
- A.τ = rF and α = τ / I
- B.F = ma and a = α r
- C.τ = rF and a = α r
- D.F = ma and τ = rF
Model answer
What a good answer should say
- τ = rF and α = τ / I
Explanation
Why this works
Define both: τ = rF gives the torque from a force at a distance; α = τ / I relates torque to angular acceleration via moment of inertia. Identify key difference: τ = rF is used to calculate torque, while α = τ / I converts that torque into angular acceleration.
Explain when each applies: first calculate torque using τ = rF, then find angular acceleration with α = τ / I. Conclude: the correct pair of equations is τ = rF and α = τ / I, which directly links force, distance, and rotational acceleration.
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