A body is accelerated by applying a force of $30\,N$. The change in the momentum of the body after $2\,sec$ is ............ $kg-m/s$ 

A rigid ball of mass $m$ strikes a rigid wall at $60^o $ and gets reflected without loss of speed as shown in the figure. The value of impulse imparted by the wall on the ball will be

A stone of mass $m$ is tied to a string of length $l$ and rotated in a circle with a constant speed $v$. If the string is released, the stone flies

A machine gun fires a bullet of mass $40\, g$ with a velocity $1200\, ms^{-1}$. The man  holding it, can exert maximum force of $144\, N$ on the gun. How many bullets can he  fire per second at the most ?

In accordance with Newton's third law of motion

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 $v ( t )= v _0^{ e ^{-1 / \tau}}$, where $v_0$ is a constant and $\tau=4 s$. The displacement of the block, in metres, at $t=\tau$ is. . . . . . . Take $e ^{-1}=0.37$