Question

A body of weight 20 N, mass 2 kg is moving in vertical circular motion with the help of a string of radius 1 m and with a velocity of 2 m/s. What is the tension in the string at the lowest point?

(a) 28 N

(b) 20 N

(c) 8 N

(d) 15 N

The question was posed to me during an internship interview.

This intriguing question originated from Uniform Circular Motion in section Motion in a Plane of Physics – Class 11

Answer 1

Right option is (a) 28 N

To elaborate: At the lowest point, the body experiences centrifugal force and the weight in the same direction, opposite to the direction of tension in the string. Centrifugal force can be calculated as mv^2/r = 8 N. Hence the tension = weight + centrifugal force = 28 N.