A 10 kg block presses against the inside wall of a hollow rotating cylinder of radius 1 m. Coefficient of friction between block and cylinder is 0.1. Find minimum angular speed to prevent the block from sliding down (g=10 m s⁻²).
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Question

A 10 kg block presses against the inside wall of a hollow rotating cylinder of radius 1 m. Coefficient of friction between block and cylinder is 0.1. Find minimum angular speed to prevent the block from sliding down (g=10 m s⁻²).

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G1 Physics · Accepted Answer

Normal reaction provides centripetal force N=mω²r. To stop downward sliding, maximum friction μN=mg. Hence μmω²r=mg, ω=√[g/(μr)]=√[10/(0.1×1)]=10 rad s⁻¹. Answer: B.