A ball of mass $10\, kg$ is moving with a velocity of $10\, m/s$. It strikes another ball of mass $5\, kg $ which is moving in the same direction with a velocity of $4 \,m/s$. If the collision is elastic, their velocities after the collision will be, respectively

Six identical balls are lined in a straight groove made on a horizontal frictionless surface.  Two similar balls each moving with a velocity $v$ collide elastically with the row of $6\, balls$ from left. What will happen ?

In an elastic collision of two particles the following is conserved

Two masses $m_1$ and $m_2$ are connected by a string of length $l$. They are held in a horizontal plane at a height $H$ above two heavy plates $A$ and $B$ made of different material placed on the floor. Initially distance between two masses is $a < l$. When the masses are released under gravity they make collision with $A$ and $B$ with coefficient of restitution $0.8$ and $0.4$ respectively. The time after the collision when the string becomes tight is :- (Assume $H>>l$)

A body dropped from a height $1\,m$ on a floor rises to a height $25\,cm$ after first  rebound. The coefficient of restitution is :-

A particle of mass $m$ strikes elastically on a wall with velocity $v$, at an angle of $60^{\circ}$ from the wall then magnitude of change in momentum of ball along the wall is