$A$ particle is acted upon by a constant power. Then, which of the following physical quantity remains constant?

$A$ 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:

The power of a pump,which can pump $500 \,kg$ of water to a height of $100 \,m$ in $10 \,s$,is .......... $kW$. (Take $g = 10 \,m/s^2$)

$A$ body of mass $1 \ kg$ starts from rest and moves with uniform acceleration. In $2 \ s$,its velocity is $10 \ m/s$. The power exerted on the body in $1 \ s$ is (in $W$)

If $\overrightarrow{F} = (60 \hat{i} + 15 \hat{j} - 3 \hat{k}) \; N$ and $\overrightarrow{V} = (2 \hat{i} - 4 \hat{j} + 5 \hat{k}) \; m/s$,then the instantaneous power is: (in $; W$)

$A$ force applied by an engine of 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 ........... $MW$.