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

12 J 4 J 8 J 9 J

4 J

vcm = 20 cm/s = 0.20 ms Work required to stop the hoop = Rotational kinetic energy + Translational kinetic energy Work required = 12 Iω2+12Mv2cm = 4 J.