Question

A stone of mass m, tied to one end of string , is moving in a horizontal circle. The length of string is gradually reduced in such a manner that the instantaneous tension T in string is T = k/r³ where k is a constant. For the motion, the quantity that remains constant is

(1) Kinetic energy

(2) Linear momentum

(3) Angular momentum

(4) Speed

Answer 1

(3) Angular momentum

The instantaneous tension, T, in string is

The instantaneous angular momentum of particle is mvr. Obviously this is a constant.