If a force of $250\, N$ acts on a body,the momentum acquired is $125\, kg \cdot m/s$. What is the period for which the force acts on the body? ......... $s$

Two particles of masses $m_1$ and $m_2$ in projectile motion have velocities $\vec{v}_1$ and $\vec{v}_2$ respectively at time $t = 0$. They collide at time $t_0$. Their velocities become $\vec{v}_1'$ and $\vec{v}_2'$ at time $2t_0$ while still moving in air. The value of $|(m_1\vec{v}_1' + m_2\vec{v}_2') - (m_1\vec{v}_1 + m_2\vec{v}_2)|$ is

$A$ ping-pong ball of mass $m$ is floating in air by a jet of water emerging out of a nozzle. If the water strikes the ping-pong ball with a speed $v$ and just after collision the water falls dead,the rate of flow (in $kg/s$) of water in the nozzle is equal to

$A$ $150\, g$ tennis ball coming at a speed of $40\, m/s$ is hit straight back by a bat to a speed of $60\, m/s$. The magnitude of the average force $F$ on the ball,when it is in contact for $5\, ms$,is ........... $N$.

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 .......... $kg \,m \,s^{-1}$.

$A$ 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).