Question

A ball having velocity v towards right and having angular velocity clockwise approaches the wall. It collides elastically with wall and moves towards left. Ground and wall are frictionless . Select the correct statement about angular velocity of the ball after collision.

(A) It will be clockwise

(B) It will be anticlockwise

(C) It becomes zero

(D) Angular speed decreases

Answer 1

Correct option (A ) It will be clockwise

Explanation:

A collision is elastic ,so after collision ball moves towards left with speed v .A walls and ground are smooth ,there is no tangential torque on the ball. Only normal forces and mg force pass through the centre of the ball ,so their torques about the centre are zero. Torques on the ball about its centre is zero . By τ=lα angular acceleration is zero hence angular velocity does not change.