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?

4Nm

Explanation:

Work done is force times distance.

The force is given as mass x (speed) ^2 / raduis. Expressed mathematically we have;

Mv^2/r

Then for the slightest measurable distance r we have: the work done as;

Mv^2/r * r

= Mv^2

= 100 * 0.2 * 0.2 = 4Nm