Question

A hook of radius 2m weighs 100kg. It rolls along a horizontal floor so that its centre if mass has a speed of 20cm/s. How much work has to be done to stop it?

(a) 5 J

(b) 6 J

(c) 2 J

(d) 4 J

This question was addressed to me during a job interview.

Asked question is from Angular Momentum topic in chapter System of Particles and Rotational Motion of Engineering Physics I

Answer 1

The correct option is (d) 4 J

The explanation is: vcm=20cm/s = 0.20ms

Work required to stop the hoop = Rotational kinetic energy+Traslational kinetic energy

Work required = \(\frac{1}{2} Iω^2+\frac{1}{2} Mv_{cm}^2  = 4J\).