An electric motor exerts a force of $40\, N$ on a cable and pulls it by a distance of $30\, m$ in one minute. The power supplied by the motor is .............. $W$

$A$ 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 $m$):

The blades of a windmill sweep out a circle of area $A$.
$(a)$ If the wind flows at a velocity $v$ perpendicular to the circle,what is the mass of the air passing through it in time $t?$
$(b)$ What is the kinetic energy of the air?
$(c)$ Assume that the windmill converts $25\%$ of the wind's energy into electrical energy,and that $A=30\;m^{2}, v=36\;km/h$ and the density of air is $1.2\;kg\;m^{-3}.$ What is the electrical power produced?

$A$ train of mass $10^6 \ kg$ is moving at a constant speed of $108 \ km/h$. If the frictional force acting on it is $0.5 \ N$ per $100 \ kg$,then the power of the train is (in $kW$)

$A$ body of mass $2 \ kg$ begins to move under the action of a time-dependent force given by $\overrightarrow{F} = (6t \hat{i} + 6t^2 \hat{j}) \ N$. The power developed by the force at time $t$ is given by:

$A$ $60 \ kg$ man runs up a staircase in $12 \ s$ while a $50 \ kg$ man runs up the same staircase in $11 \ s$. The ratio of the rate of doing their work is: