A body falling from a height of $10\,m$ rebounds from hard floor. If it loses $20\%$ energy in the impact, then coefficient of restitution is

Four particles $A, B, C$  and $D$  of equal mass are placed at four corners of a square. They move with equal uniform speed  $v$  towards the intersection of the diagonals. After collision, $A$  comes to rest, $B$ traces its path back with same speed and $C$ and $D$ move with equal speeds. What is the velocity of $C$  after collision

A ball impinges directly on a similar ball at rest. If $1/4^{th}$ of the kinetic energy is lost by the impact, the value of coefficient of restitution is

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?

Two masses of $0.25\, kg$ each moves towards each other with speed $3\, ms^{-1}$ and $1\, ms^{-1}$. Then they collide and stick together. Find the final velocity .............. $\mathrm{m} \mathrm{s}^{-1}$

A particle of mass $m$ collides with a heavy mass (at rest) elastically and after collision returns with $4/9$ of it's initial kinetic energy. The mass of heavy object is ............... $\mathrm{m}$