$A$ body whose momentum is constant must have constant

$A$ ball of mass $50 \,g$ is dropped from a height of $20 \,m$. $A$ boy on the ground hits the ball vertically upwards with a bat with an average force of $200 \,N$,so that it attains a vertical height of $45 \,m$. The time for which the ball remains in contact with the bat is ........... of a second. [Take $g = 10 \,m/s^2$]

$A$ particle is acted upon by a force whose components' variations with time are shown in the diagrams. The magnitude of the change in momentum of the particle in $0.1\,s$ is:

$A$ mass of $100\,g$ strikes the wall with a speed of $5\,m/s$ at an angle as shown in the figure and it rebounds with the same speed. If the contact time is $2 \times 10^{-3}\,s$,what is the force applied on the mass by the wall?

$A$ ball of mass $3 \ kg$ strikes a wall at an angle of $60^\circ$ with a velocity of $10 \ m/s$ and rebounds at the same angle and speed. What is the change in momentum of the ball in $MKS$ units?

$A$ ball of mass $m$ moves with speed $v$ and strikes a wall normally and is reflected back normally. If its time of contact with the wall is $t$,find the force exerted by the ball on the wall.