Question

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

Answer 1

The Block is moving the rim of the pulley
The pulley is moving at a ω = 10 rad/s
Therefore the radius of the pulley = 20 cm
Therefore linear velocity on the rim = tangential velocity = rω
= 20 × 20 = 200 cm/s = 2 m/s.