A wheel having moment of inertia `2 kg m^(2)` about its vertical axis, rotates at the rate of `60 rpm` about this axis. The torque which can stop the wheel's rotation in one minute would be

Options

A. `pi/12` N-m
B. `pi/15` N-m
C. `pi/18` N-m
D. `(2pi)/15` N-m

Answer

B

Explanation

From `tau =Ialpha` and `omega=omega_0+alpha t`
Here `omega_0 =(60xx2pi)/60` rad/sec. = `2pi` rad/sec.
`tau=I(omega_0/I)=2xx(2pi)/60 = pi/15 N-m`