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?

2 J

Explanation:

Work = change in energy

W = ΔKE

W = ½ mv²

W = ½ (100 kg) (0.2 m/s)²

W = 2 J

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

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