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

$A$ vehicle of mass $m$ starts from rest and accelerates. If the engine delivers a constant power $p$,what is the velocity of the vehicle at time $t$?

Which of the following must be known in order to determine the power output of an automobile?

$A$ particle is moving unidirectionally on a horizontal plane under the action of a constant power supplying energy source. The displacement $(s)$ - time $(t)$ graph that describes the motion of the particle is (graphs are drawn schematically and are not to scale)

$A$ pump on the ground floor of a building can pump up water to fill a tank of volume $36 \,m^3$ in $30 \,min$. If the tank is $50 \,m$ above the ground, and the electric power consumed by the pump is $40 \,kW$, the efficiency of the pump is (Use $g=10 \,m / s^2$ and density of water $=1000 \,kg / m^3$ ) (in $\%$)

$A$ 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 $MW$)