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?

• A. 2 m/s
• B. 0.2 m/s
• C. 20 m/s
• D. 20 cm/s

Answer 1

The correct option is A

2 m/s

The Block is moving the rim of the pulley

The pulley is moving at $\omega$ = 10 rad/s

The radius of the pulley = 20 cm

Therefore linear velocity on the rim = tangential velocity = $r\omega$

= 2 m/s.