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 5 m/s. What is the tension in the string when is horizontal?

(a) 30 N

(b) 50 N

(c) 20 N

(d) 25 N

I got this question in an interview for internship.

The above asked question is from Uniform Circular Motion topic in chapter Motion in a Plane of Physics – Class 11

Answer 1

Correct choice is (b) 50 N

For explanation: When the string is horizontal, the tension in the string and the centrifugal force are opposite to each other. Centrifugal force can be calculated as mv^2/r = 50 N. Hence the tension = centrifugal force = 50 N.