$A$ bal $A$ collides elastically with another identical ball $B$ initially at rest $A$ is moving with velocity of $10m/ s$ at an angle of $60^o$ from the line joining their centres. Select correct alternative :

A stream of glass beads, each with a mass of $15\  gram$, comes out of a horizontal tube at a rate of $100\  per second$. The beads fall a distance of $5\  m$ to a balance pan and bounce back to their original height. How much mass(in $kg$) must be placed in the other pan of the balance to keep the pointer at zero?

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

A body falling on the ground from $a$ height of $10\, m$, rebounds to a height $2.5\, m,$ then the ratio of the velocities of the body just before and after the collision will be

A sphere of mass $m $ moving with a constant velocity $u$ hits another stationary sphere of the same mass. If $e$  is the coefficient of restitution, then the ratio of the velocity of two spheres after collision will be

$A$ flexible chain of length $2m$ and mass $1kg$ initially held in vertical position such that its lower end just touches a horizontal surface, is released from rest at time $t = 0$. Assuming that any part of chain which strikes the plane immediately comes to rest and that the portion of chain lying on horizontal surface does not from any heap, the height of its centre of mass above surface at any instant $t = 1/\sqrt 5$ befor it completely comes to rest) is ................ $\mathrm{m}$