Question

A circular platform is mounted on a frictionless vertical axle. Its radius R = 2m and its moment of inertia about the axle is 200 kgm² . it is initially at rest. A 50 kg man stands on the edge of the platform and begins to walk along the edge at the speed of 1ms^–1 relative to the ground. Time taken by the man to complete one revolution with respect to disc is : 

(A) πs  

(B) 3π / 2 s

(C) 2π s 

(D)  π / 2 s

Answer 1

Correct option:  2π s

Explanation:

using angular momentum conservation

L_i = 0

L_t = mvR – Iω

mvR =  I.ω

ω = ( 1/2)

(v + ω R)t = 2π R