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 at the highest point?

(a) 30 N

(b) 50 N

(c) 20 N

(d) 25 N

The question was posed to me in examination.

The doubt is from Uniform Circular Motion topic in division Motion in a Plane of Physics – Class 11

Answer 1

Correct choice is (a) 30 N

To elaborate: At the highest point, the tension and the weight are in the same direction but the centrifugal force is in the opposite direction. Centrifugal force can be calculated as mv^2/r = 50 N. Hence the tension = centrifugal force-weight = 30 N.