As the system is initially at rest, therefore, initial angular momentum Li=0. According to the principle of conservation of angular momentum, final angular momentum, Lf=0. ∴ Angular momentum of disc = Angular momentum of man is in opposite direction of platform. i.e., mvR=Iω or ω=
mvR
I
=
50×1×2
200
=
1
2
rads−1 Angular velocity of man relative to platform is or ωr=ω+
υ
R
=
1
2
+
1
2
=1rads−1 Time taken by the man to complete one revolution is T=
