At any instant of time $t$, the displacement of a particle is given by $x = 2t - 1$ ($SI$ units) under the influence of a force of $5 \,N$. The value of instantaneous power is (in $SI$ units):

Air strikes the blades of a windmill with a speed of $v$. The power generated is proportional to which of the following?

$A$ body moves along a straight line due to a constant power delivered by a machine. The distance covered by the body in time $t$ is proportional to:

$A$ force of $(2\hat i + 3\hat j + 4\hat k) \text{ N}$ acts on a body for $4 \text{ s}$ and produces a displacement of $(3\hat i + 4\hat j + 5\hat k) \text{ m}$. The power used is ............. $\text{W}$. (in $.5$)

$A$ body moves along a straight line under the action of a constant power delivered by an engine. The distance covered by the body in time $t$ is proportional to:

Two men have a weight ratio of $5 : 3$. If the ratio of the time taken by them to climb stairs is $11 : 9$,find the ratio of their power.