A ball is attached to a string that is attached to a pole. When the ball is hit, the string wraps around the pole and the ball spirals inwards sliding on the frictionless surface. Neglecting air resistance, what happends as the ball swings around the pole?

Options

A. the mechanical energy and angular momentum are conserved
B. the angular momentum of the ball is conserved and the mechanical energy of the ball increased
C. the angular momentum of the ball is conserved and the mechanical energy of the ball decreased
D. the mechanical energy the ball is conserved and angular momentum of ball decreases

Answer

D

Explanation

Torque of tension about `O` is inward (clockwise sense) therefore angular momentum decrease.