$A$ light particle moving horizontally with a speed $v_1$ strikes a very heavy block moving in the same direction with a speed $v_2$. The collision is elastic. After the collision,the velocity of the particle is:

Two balls $A$ and $B$,of masses $M$ and $2M$ respectively,collide with each other. If ball $A$ moves with a speed of $150 \ m \ s^{-1}$ and collides with ball $B$ moving with speed $v$ in the opposite direction,and after the collision ball $A$ comes to rest with the coefficient of restitution being $1$,then the speed of ball $B$ before it collides with ball $A$ is: (in $m \ s^{-1}$)

Two identical spheres $A$ and $B$ collide with two other identical spheres $C$ and $D$ with the same velocity $v$. What happens after the collision?

When two particles collide elastically,then impulsive force can't change

$A$ billiard ball of mass $M$,moving with velocity $v_1$ collides with another ball of the same mass but at rest. If the collision is elastic,the angle of divergence after the collision is (in $^{\circ}$)

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Body $P$ having mass $M$ moving with speed $u$ has a head-on elastic collision with another body $Q$ having mass $m$ initially at rest. If $m << M$,body $Q$ will have a maximum speed equal to $2u$ after the collision.
Reason $R$: During an elastic collision,the momentum and kinetic energy are both conserved.
In the light of the above statements,choose the most appropriate answer from the options given below: