Two balls of mass $5 \ kg$ are moving in opposite directions with the same speed of $5 \ m/s$. They undergo a head-on elastic collision. Find the final velocity of the balls in $m/s$.

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?

Assertion $(A)$: In an elastic collision between two bodies,the relative speed of the bodies after collision is equal to the relative speed before the collision.
Reason $(R)$: In an elastic collision,the linear momentum of the system is conserved.

$A$ particle of mass $m_1$ collides with a particle of mass $m_2$ at rest. After the elastic collision,the two particles move at an angle of $90^{\circ}$ with respect to each other. The ratio $\frac{m_2}{m_1}$ is

Which of the following potential energy curves in the figure cannot possibly describe the elastic collision of two billiard balls? Here $r$ is the distance between the centres of the balls.

$A$ billiard ball moving with a speed of $5 \, m/s$ collides with an identical ball originally at rest. If the first ball stops after collision,then the second ball will move forward with a speed of ........... $m/s$.