Two bodies having same mass $40\, kg$ are moving in opposite directions,one with a velocity of $10\, m/s$ and the other with $7\, m/s$. If they collide and move as one body,the velocity of the combination is ........ $m/s$.

$A$ body falls freely from a height of $100 \ m$ onto the ground and rebounds to a maximum height of $36 \ m$ after collision. The coefficient of restitution between the ground and the body is

$A$ bullet of mass $m$ and speed $v$ hits a pendulum bob of mass $M$ at time $t_1$,and passes completely through the bob. The bullet emerges at time $t_2$ with a speed of $v/2$. The pendulum bob is suspended by a stiff rod of length $l$ and negligible mass. After the collision,the bob can barely swing through a complete vertical circle. At time $t_3$,the bob reaches the highest position. What quantities are conserved in this process?

$A$ cricket ball hits the ground with a speed of $5 \,m \,s^{-1}$ making an angle of $30^{\circ}$ with the horizontal. If the coefficient of restitution is $0.2$, the speed of the reflected ball in $m \,s^{-1}$ is

$A$ ball is dropped from a height $h$. As it bounces off the floor,its speed is $80$ percent of what it was just before it hit the floor. The ball will then rise to a height of most nearly .............. $h$.

$A$ ball is thrown with a velocity of $6\, m/s$ vertically downwards from a height $H = 3.2\, m$ above a horizontal floor. If it rebounds back to the same height,then the coefficient of restitution $e$ is $[g = 10\, m/s^2]$.