A truck weighing 1000 kgf changes its speed from 36 km $h^{-1}$ to 72 km $h^{-1}$ in 2 minutes.Calculate:(i) the work done by the engine,and (ii) its power.(g=10 m$s^{-2}$)

(i) Mass of the truck = 1000 kg

Initial velocity, $u=36kmph=36\times \frac{5}{18}m/s=10m/s$

Final velocity, $v=72kmph=20m/s$

Work done = Change in kinetic energy $=\frac{1}{2}m(v^2-u^2)=\frac{1}{2}\times 1000\times ({20}^2-{10}^2)=1.5\times {10}^{5}J$

(ii) Power $=\frac{Workdone}{Time}=\frac{1.5\times {10}^5}{120}=1250W$