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 kg m^(2)`. It is initially at rest. A `50 kg` man stands on the edge at 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 is :
A. `(3pi)/(2)s`
B. `2pis`
C. `(pi)/(2)s`
D. `pis`

Answer 1

Correct Answer - B
`I_(1)omega_(1)+I_(2)omega_(2)=0`
`200((1)/(2))+200omega_(2)=0`
`omega_(2)=-(1)/(2)`
`omega_(R)=omega_(1)-omega_(2)=1"rad/sec"`
`T=(2pi)/(omega)=2pisec`