$N$ bullets,each of mass $m \, kg$,are fired with a velocity $v \, m/s$ at the rate of $n$ bullets per second upon a wall. The reaction force offered by the wall to the bullets is given by:

$A$ particle is acted upon by a force whose components' variations with time are shown in the diagrams. The magnitude of the change in momentum of the particle in $0.1\,s$ is:

$A$ body of mass $M$ collides against a wall with a velocity $v$ and retraces its path with the same speed. The change in momentum is (take initial direction of velocity as positive).

$A$ particle moves in the $x-y$ plane under the action of a force $\overrightarrow{F}$ such that the value of its linear momentum $\overrightarrow{P}$ at any time $t$ is $P_x = 2\cos t$ and $P_y = 2\sin t$. The angle $\theta$ between $\overrightarrow{F}$ and $\overrightarrow{P}$ at a given time $t$ will be $\theta = $ ........... $^o$.

$A$ body of $2\, kg$ has an initial speed of $5\, ms^{-1}$. $A$ force acts on it for some time in the direction of motion. The force-time graph is shown in the figure. Find the final speed of the body in $ms^{-1}$.

Consider the following statement: When jumping from some height,you should bend your knees as you come to rest,instead of keeping your legs stiff. Which of the following relations can be useful in explaining the statement?