$A$ $750 \,W$ motor drives a pump which lifts $300 \,L$ of water per minute to a height of $6 \,m$. The efficiency of the motor is nearly (Take,acceleration due to gravity to be $10 \,m/s^2$) (in $\%$)

$A$ lift raises $50$ passengers, each having an average weight of $600 \,N$, to a height of $100 \,m$ at a constant speed in time $t$. If the average power of $15 \,kW$ is required by the lift, then the value of $t$ in seconds is:

An elevator can carry a maximum load of $1800 \; kg$ (elevator $+$ passengers) and is moving up with a constant speed of $2 \; m s^{-1}$. The frictional force opposing the motion is $4000 \; N$. Determine the minimum power delivered by the motor to the elevator in watts as well as in horsepower.

An engine is dragging a mass of $5000 \ kg$ with a velocity of $5 \ ms^{-1}$ along a smooth inclined plane of inclination $1$ in $50$. Then the power of the engine is (in $kW$)

$A$ body of mass $1\, kg$ begins to move under the action of a time-dependent force $\overrightarrow{F} = (2t\hat{i} + 3t^2\hat{j})\, N$,where $\hat{i}$ and $\hat{j}$ are unit vectors along the $x$ and $y$ axes. What power will be developed by the force at time $t$?

$A$ man is riding a cycle with a velocity of $7.2 \text{ km/hr}$ up a hill having a slope of $1$ in $20$. The total mass of the man and the cycle is $100 \text{ kg}$. The power of the man is ............ $\text{W}$. (in $\text{ W}$)