If $n$ balls hit elastically and normally on a surface per unit time and all balls of mass $m$ are moving with the same velocity $u$, then the force on the surface is ..........

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

$A$ smooth sphere $A$ is moving on a frictionless horizontal plane with angular speed $\omega$ and center of mass with velocity $v$. It collides elastically and head-on with an identical sphere $B$ at rest. Neglect friction everywhere. After the collision,their angular speeds are $\omega_A$ and $\omega_B$ respectively. Then

$A$ ball falls from a height of $5\,m$ and strikes the roof of a lift. If at the time of collision,the lift is moving in the upward direction with a velocity of $1\,m/s$,then the velocity with which the ball rebounds after collision will be (assume $e = 1$):

$A$ particle of mass $m$ moving with a velocity $\vec{V}$ makes a head-on elastic collision with another particle of the same mass initially at rest. The velocity of the first particle after the collision will be:

Three blocks are initially placed as shown in the figure. Block $A$ has mass $m$ and initial velocity $v$ to the right. Block $B$ with mass $m$ and block $C$ with mass $4m$ are both initially at rest. Neglect friction. All collisions are elastic. The final velocity of block $A$ is