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Laws of Motion
Friction and Circular Motion
1 question from 1 paper, each with its answer.
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- years asked, 2017–2026
- 1 of 10
- of Laws of Motion
- 1.39%
Concepts tested
- minimum angular speed to keep a block against a rotating wall
All Questions
2019 1 question
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A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be: ($g=10\ m/s^2$)The normal reaction from the wall provides the centripetal force: $N=mr\omega^2$ For equilibrium of the block, limiting friction must balance weight: $f_L=\mu N\ge mg$ $\mu mr\omega^2\ge mg\Rightarrow\omega\ge\sqrt{\frac{g}{\mu r}}$ $\omega_{min}=\sqrt{\frac{10}{0.1\times1}}=10\ rad/s$