The force exerted by the floor of an elevator on the foot of a person standing there, is more than his weight, if the elevator is

If E, G and N represents the magnitudes of electromagnetic, gravitational and nuclear forces between two electrons at a given separation, then,

For an inelastic collision, the value of e is

A perfect inelastic body collides head-on with a wall with a velocity $vv$. The change in momentum is

Two masses ma and mb moving with velocitics $v_{a}v\_a$ and $v_{b}v\_b$ in opposite direction collide elastically and after the collision $m_{a}m\_a$ and $m_{b}m\_b$ move with velocities $v_{b}v\_b$ and $v_{a}v\_a$ respectively. Then the ratio $m_{a}m\_a$ $m_{b}m\_b$ is

The frictional force acts _____.

A marble of mass X collides with a block of mass Z, with a velocity Y. and sticks to it. The final velocity of the system is

Two balls lying on the same plane collide. Which of the following will be always conserved?

A body is moving with uniform velocity of 50 km h , the force required to keep the body in motion in SI unit is

A coolie holding a suitcase on his head of 20 kg and travels on a platform. then work done in joule by the coolie is