A neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is

The force $F$ acting on a body moving in a circle of radius $r$ is always perpendicular to  the instantaneous velocity $v$. The work done by the force on the body in one complete  rotation is : 

A mass $m$ slips along the wall of a semispherical surface of radius $R$. The velocity at the bottom of the surface is

Two ice skaters $A$ and $B$ approach each other at right angles. Skater $A$ has a mass $30\,kg$ and velocity $1\,m/s$ and skater $B$ has a mass $20\,kg$ and velocity $2\,m/s$ . They meet and cling together. Their final velocity of the couple is ............. $\mathrm{m}/ \mathrm{s}$

A body is dropped from a height $h$ . If it acquires a momentum $p$ just before striking the ground, then the mass of the body is

A ball is dropped from height $h$ on a plane. If the coefficient of restitution of the plane is $e$ and if ball hits ground two times, the height upto which it reaches after two jumps, will be