NEET 2019 · PhysicsCentripetalPrevious Year Question
A block of mass 10 kg is in contact with the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the wall is 0.1. The minimum angular velocity of the drum (rotating about its vertical axis) needed to keep the block stationary is (g = 10 m/s²):
Answer: (C) 10 rad/s. Correct Answer (C) Solution: Wall provides centripetal normal force N = mω²R; friction must support weight: μN ≥ mg.
- A.√10 rad/s
- B.(√10)/2 rad/s
- C.10 rad/s✓
- D.10π rad/s
Correct Answer
(C) 10 rad/s
Solution & Explanation
Correct Answer (C) Solution: Wall provides centripetal normal force N = mω²R; friction must support weight: μN ≥ mg. Minimum: μmω²R = mg ⇒ ω = √(g/μR) = √(10/(0.1×1)) = √100 = 10 rad/s.
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