Essential University Physics: Volume 1 (3rd Edition)

a) $77 \ J$ b) $89.8\ W$
a) We know that work is equal to the integral of torque. Thus, we obtain: $W=\int_0^{\frac{\pi}{\omega}}\tau_0\omega sin\omega t dt$ $W=2\tau_0=2\times 38.5 = 77 \ J$ b) We know that power is equal to the energy over the the change in time. Since Joules is an SI unit, we know we must convert rpm to rotations per second to find the average power over the one rotation: $P=\frac{77}{.857}=89.8\ W$