$A$ body of mass $2 \, kg$ collides with a wall with a speed of $100 \, m/s$ and rebounds with the same speed. If the time of contact was $1/50 \, s$,the force exerted on the wall is:

$A$ machine gun fires a bullet of mass $40$ g with a speed of $600$ m/s. The person holding the gun can bear a maximum force of $168$ $N$ on it. The number of bullets that can be fired from the gun per second is

Displacement of a particle of mass $2\, kg$ moving in a straight line varies with time as $s = (2t^3 + 2)\, m$. The impulse of the force acting on the particle over a time interval between $t = 0$ and $t = 1\, s$ is .......... $N-s$.

In the figure given below,the position-time graph of a particle of mass $0.1 \,kg$ is shown. The impulse at $t = 2 \,s$ is .......... $kg \,m \,s^{-1}$.

$A$ solid horizontal surface is covered with a thin layer of oil. $A$ rectangular block of mass $m = 0.4 \ kg$ is at rest on this surface. An impulse of $1.0 \ N \ s$ is applied to the block at time $t = 0$ so that it starts moving along the $x$-axis with a velocity $v(t) = v_0 e^{-t/\tau}$,where $v_0$ is a constant and $\tau = 4 \ s$. The displacement of the block,in metres,at $t = \tau$ is. . . . . . . Take $e^{-1} = 0.37$.

The time in which a force of $2 \, N$ produces a change of momentum of $0.4 \, kg \cdot m/s$ in a body is ......... $s$.