The force required to row a boat at constant velocity is proportional to the square of its speed. If a speed of $v \, km/h$ requires $4 \, kW$ of power,how much power does a speed of $2v \, km/h$ require?

The power of a water pump is $4 \,kW$. If $g = 10 \,m/s^2$,the amount of water it can raise in $1 \,minute$ to a height of $20 \,m$ is ........... $litres$.

$A$ car of mass $1200 \,kg$ (together with the driver) is moving with a constant acceleration of $2 \,m/s^2$. How much power does the engine generate at the instant when the speed reaches $20 \,m/s$ (in $\,W$)? (Assume that the coefficient of friction between the car and the road is $0.5$ and $g = 10 \,m/s^2$).

The power of a pump,which can pump $200 \ kg$ of water to a height of $50 \ m$ in $10 \ s$,will be:

$A$ body of mass $4 \ kg$ is placed on a plane at a point $P$ having coordinates $(3, 4) \ m$. Under the action of force $\overrightarrow{F} = (2 \hat{i} + 3 \hat{j}) \ N$,it moves to a new point $Q$ having coordinates $(6, 10) \ m$ in $4 \ s$. The average power and instantaneous power at the end of $4 \ s$ are in the ratio of:

$A$ force of $5 \,N$ acts on a body initially at rest. If the instantaneous power due to the force at the end of the third second $(t=3 \,s)$ is $5 \,W$, then the mass of the body is (in $\,kg$)