Class 11 NEET Physics System of Particles and Rotational Motion

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 = Angular momentum of man of platform in opposite direction
i.e., mvR=Iω
or ω=

mvR

I

=

50×1×2

200

=

1

2

rads−1
Angular velocity of man relative to platform is
ωr=ω+

v

R

=

1

2

+

1

2

=1rads−1
Time taken by the man to complete one revolution is
T=

2π

ωr

=

2π

1

=2πs