$A$ body of mass $3\,kg$ is acted on by a force which varies as shown in the graph below. The momentum acquired is given by ........... $N-s$.

In an hour-glass,approximately $100$ grains of sand fall per second (starting from rest); and it takes $2 \, s$ for each sand particle to reach the bottom of the hour-glass. If the average mass of each sand particle is $0.2 \, g$,then the average force exerted by the falling sand on the bottom of the hour-glass is close to .......... $N$.

$Assertion$ : $A$ quick collision between two bodies is more violent than a slow collision,even when the initial and final velocities are identical.
$Reason$ : The rate of change of momentum is greater in the first case.

$A$ jet of water with cross-sectional area $A$ strikes a wall at an angle $\theta$ with the normal to the wall and rebounds elastically. If the density of water is $\rho$ and the velocity is $v$,what is the force exerted on the wall?

$A$ body of mass $M$ hits normally a rigid wall with velocity $V$ and bounces back with the same velocity. The impulse experienced by the body is

$A$ stream of glass beads, each with a mass of $15 \ g$, comes out of a horizontal tube at a rate of $100 \ \text{beads per second}$. The beads fall a distance of $5 \ m$ to a balance pan and bounce back to their original height. How much mass (in $kg$) must be placed in the other pan of the balance to keep the pointer at zero?