$A$ ball is dropped from a height of $20\,m$. If the coefficient of restitution for the collision between ball and floor is $0.5$,after hitting the floor,the ball rebounds to a height of $.............m$.

$A$ ball is moving with velocity $4 \ m/s$ and collides head-on with another stationary ball of double the mass. If the coefficient of restitution is $0.2$,then their velocities (in $m/s$) after the collision will be:

$A$ uniform rod of mass $M$ and length $L$ is placed on a smooth horizontal surface. $A$ particle of mass $m$ strikes the rod at one end with a velocity $v$ perpendicular to the rod. If the particle comes to rest after the collision,the velocity of the center of mass of the rod after the collision is:

$A$ ball strikes a smooth horizontal ground at an angle of $45^o$ with the vertical. What cannot be the possible angle of its velocity with the vertical after the collision? (Assume $e \leq 1$ ).

$A$ moving block having mass $m$ collides with another stationary block having mass $4m$. The lighter block comes to rest after the collision. If the initial velocity of the lighter block is $v$,then the value of the coefficient of restitution $(e)$ will be:

$A$ sphere collides with another sphere of identical mass. After collision,the two spheres move. The collision is inelastic. Then the angle between the directions of the two spheres is