Two men with weights in the ratio $4:3$ run up a staircase in time in the ratio $12:11$. The ratio of power of the first to that of second is

Why is electrical power required at all when the elevator is descending? Why should there be a limit on the number of passengers in this case?

An automatic gun fires $360$ bullets per minute with a speed of $360 \,km/h$. If each bullet weighs $20 \,g$,the power of the gun is (in $\,W$)

Water falls from a waterfall onto the blades of a turbine at a rate of $100 \ kg/s$. If the height of the fall is $100 \ m$,what is the power generated by the turbine?

$A$ body of mass $2\, kg$ is driven by an engine delivering a constant power $1\, J/s$. The body starts from rest and moves in a straight line. After $9$ seconds,the body has moved a distance (in $m$):

An engine pumps water through a hose pipe. Water passes through the pipe and leaves it with a velocity of $2\, m/s$. The mass per unit length of water in the pipe is $100\, kg/m$. Calculate the power $W$ of the engine. (in $, W$)