$A$ man does a given amount of work in $10 \ s$. Another man does the same amount of work in $20 \ s$. The ratio of the output power of the first man to the second man is:

$A$ motor boat is travelling with a speed of $3.0\, m/s$. If the force on it due to water flow is $500\, N$,the power of the boat is

$A$ $60\; HP$ electric motor lifts an elevator having a maximum total load capacity of $2000\; kg$. If the frictional force on the elevator is $4000\; N$,the speed of the elevator at full load is close to .............. $m/s$.
$(1\; HP = 746\; W, g = 10\; ms^{-2})$

$1\,kWh$ is a unit of power. This statement is true or false? If it is wrong,then correct it.

An engine develops $10 \text{ kW}$ of power. How much time will it take to lift a mass of $200 \text{ kg}$ to a height of $40 \text{ m}$? $(g = 10 \text{ m/s}^2)$

$A$ force applied by an engine on a train of mass $2.05 \times 10^6 \ kg$ changes its velocity from $5 \ m/s$ to $25 \ m/s$ in $5 \ minutes$. The power of the engine is (in $MW$)