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

Options

A. 4.8 J
B. 4.0 J
C. 6.2 J
D. 7.2 J

Explanation

b) Given, R= 2m, M = 100 kg
Speed of center of mass,
`v=20cm/s = 0.20 m/s`
Work done to stop the loop = Total kinetic energy of the hoop
`W= 1/2Mv^(2)+1/2(Mr^(2))xx (v^(2)/R^(2))`
`= 1/2 Mv^(2) + 1/2Mv^(2) = Mv^(2)`
`100 xx (0.20)^(2) = (100 xx 0.04)J` = 4.0 J