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Class 11
Physics :-NCERT Solutions - SYSTEM OF PARTICLES AND ROTATIONAL MOTION

Page No 179:
Question 7.19:
A hoop of radius 2 m weighs 100 kg. It rolls along a horizontal floor so that its centre of mass has a speed of 20 cm/s. How much work has to be done to stop it?


Answer:

Radius of the hoop, r = 2 m

Mass of the hoop, m = 100 kg

Velocity of the hoop, v = 20 cm/s = 0.2 m/s

Total energy of the hoop = Translational KE + Rotational KE

Moment of inertia of the hoop about its centre, mr2

The work required to be done for stopping the hoop is equal to the total energy of the hoop.

∴Required work to be done, W = mv= 100 × (0.2)= 4 J


SET

NCERT Physics Class 11