Two men each of mass m stand on the rim of a horizontal circular disc, diametrically opposite to each other. The disc has a mass M and is free to rotate about a vertical axis passing through its centre of mass. Each mass start simultaneously along the rim clockwise and reaches their original starting positions on the disc. The angle turned through by disc with respect to the ground (in radian) is

Options

A. `(8m pi)/(4m + M)`
B. `(2m pi)/(4m + M)`
C. `(m pi)/(M + m)`
D. `(4m pi)/(2M + m)`

Answer

A

Explanation

`2(mR^(2))(2pi -theta) =1/2MR^(2)theta, 4mpi - 2mtheta = M/2 theta, therefore theta=(8mpi)/(4m + M)`