Question

A particle of mass 5kg is rotating about an axis in a circle with a speed of 10m/s. What should be its radius so that the component of angular momentum about the axis is 5kgm^2/s?

(a) 0.1cm

(b) 10cm

(c) 5cm

(d) 0.5m

The question was posed to me in an online interview.

This question is from Angular Momentum in case of Rotations about a Fixed Axis in chapter System of Particles and Rotational Motion of Physics – Class 11

Answer 1

The correct option is (b) 10cm

Easiest explanation: The angular momentum of a particle along the axis is given by Iω.                                                   I = mr^2 ω = v/r, where ‘r’ is the radius of the particle.                                                                                                    Iω = mvr = 5                                                                                                                                                                                 ∴ 5*10*r = 5                                                                                                                                                                                        ∴ r = 0.1m = 10cm.