Question

A block of mass 5 Kg, exhibits circular motion with the mass decreasing at the rate of 0.5 Kg/s. At what time the centripetal force will be zero on the block?

(a) At 10 s

(b) At 5 s

(c) At 1 s

(d) At 7 s

This question was posed to me by my school teacher while I was bunking the class.

The above asked question is from Non-Uniform Circular Motion in chapter Laws of Motion of Physics – Class 11

Answer 1

The correct choice is (a) At 10 s

Explanation: The centripetal force on a body is directly proportional to its mass with a proportionality constant of 1. Hence the centripetal force will be zero when the mass is zero. The function for the mass at t seconds is m = 5 – 0.5t. On equating this to zero we get, t = 10 s. this is the required time.