The angular momentum of a wheel having a rotational inertia of 0.2 ~kg ~m ^2 about its symmetric axis decreases from 4 to 2 ~kg ~m ^2 ~s ⁻¹ in 4 ~s . The average power of the wheel is

Step-by-step solution

We have, I =0.2 ~kg / m ^2 aligned & L _ f =4 ~kg ~m ^2 ~s ⁻¹ & ~L _ i =2 ~kg ~m ^2 ~s ⁻¹ aligned aligned & L _ f = I _ f _ f = 4 0.2 =20 rad / s & L _ i = I _ i _ i = 2 0.2 =10 rad / s aligned So, power = work done time taken = K t aligned & = 1 2 0.2 20^2- 1 2 0.2 10^2 4 & =7.5 ~W aligned