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

Statement-$1$: In an elastic collision between two bodies,the relative speed of the bodies after the collision is equal to the relative speed of the bodies before the collision.
Statement-$2$: In an elastic collision,the linear momentum of the system is conserved.

Two smooth objects with a coefficient of restitution $e$ collide directly and bounce as shown. Newton's law of restitution gives:

Two billiard balls of mass $0.05\,kg$ each,moving in opposite directions with $10\,m/s$,collide and rebound with the same speed. If the time duration of contact is $t = 0.005\,s$,then the force exerted on the balls due to each other is $\dots N$.

$A$ neutron moving with velocity $u$ collides elastically with a stationary atom of mass number $A$. If the collision is head-on and the initial kinetic energy of the neutron is $E$, then the final kinetic energy of the neutron after the collision is:

An object of mass $M$ is much heavier than another object of mass $m$. The heavy object moving with speed $v$ undergoes an elastic collision with the light object at rest. What will be the speed of the light object after the collision?