Five objects of different masses are simultaneously released vertically downwards from height $h$ (in air). Which physical quantity associated with the objects will change at the instant they strike the ground? (Neglect the air resistance.)

$A$ $40 \ g$ ball dropped from a certain height bounces back from the horizontal ground without losing mechanical energy. If its speed is $10 \ m/s$ just before making contact with the ground,and the average value of the force of the ground on the ball is $16 \ N$ while the ball and ground are in contact,how long were they in contact in milliseconds $(ms)$?

$A$ ball of mass $0.1 \,kg$ strikes a wall normally with a speed of $30 \,ms^{-1}$ and rebounds with a speed of $20 \,ms^{-1}$. The impulse of the force exerted by the wall on the ball is (in $\,N-s$)

$A$ batsman hits back a ball straight in the direction of the bowler without changing its initial speed of $12 \; m/s$. If the mass of the ball is $0.15 \; kg$,determine the impulse (in $N \cdot s$) imparted to the ball. (Assume linear motion of the ball)

$A$ force is applied to a body of mass $3 \ kg$ at rest on a frictionless horizontal surface, as shown in the force-time $(F-t)$ graph. The speed of the body after $1 \ s$ is: (in $m/s$)

The momentum $p$ of an object varies with time $(t)$ as shown in the figure. The corresponding force $(F)$-time $(t)$ graph is