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Rotational Mechanics — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsRotational Mechanics3 Marks
Question
A block hangs from a string wrapped on a disc of radius 20cm free to rotate about its axis which is fixed in a horizontal position. If the angular speed of the disc is 10rad/s at some instant, with what speed is the block going down at that instant?
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Answer

The Block is moving the rim of the pulley The pulley is moving at a $\omega=10\text{rad/s}$ Therefore the radius of the pulley = 20cm Therefore linear velocity on the rim = tangential velocity $=\text{r}_{\omega}=20\times20=200\text{cm/s}=2\text{m/s}.$

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