For a hoop, disc, and solid sphere of same mass and radius rolling down an incline. Order of acceleration (fastest first):
AAll equal
BSphere > Disc > Hoop (smaller I/MR² is faster)
CDisc > Sphere > Hoop
DHoop > Disc > Sphere
Answer & Solution
Correct answer: B. Sphere > Disc > Hoop (smaller I/MR² is faster)
Acceleration in rolling: a = g sin theta / (1 + I/(MR²)). For sphere I/MR² = 2/5 (smallest); disc 1/2; hoop 1. So sphere is fastest, hoop slowest. Independent of mass and radius!
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