Physics - Rotation Question with Solution | TestHub

Since the net force on the belt is the difference between the two tensions, the torque exerted by the motor on the belt is, $$\begin{array}{rl}\tau & =Fr=(135\mathrm{N}-45\mathrm{N})(0.08\mathrm{m})\\ & =7.2\mathrm{N}\mathrm{m}\end{array}$$ The power output of the motor is therefore $$\begin{array}{rl}P& =\tau \omega =(72\mathrm{N}\cdot \mathrm{m})\left(200\mathrm{rad}{\mathrm{s}}^{-1}\right)\\ & =1440\mathrm{W}=1.44\mathrm{kW}\end{array}$$