A body of mass 0.25 kg travels along a straight line from $x=0$ to $x=2 \mathrm{~m}$ with a speed $v=k x^{3 / 2}$ where $k$ $=2 \mathrm{SI}$ units. The work done by the net during this displacement is

A particle of mass 500 g is at rest. It is free to move along a straight line. The power delivered to the particle varies with time according to the following graph

The momentum of the particle at $t=5$ s is

A ball of mass $$0.2 \mathrm{~kg}$$ is thrown vertically down from a height of $$10 \mathrm{~m}$$. It collides with the floor and loses $$50 \%$$ of its energy and then rises back to the same height. The value of its initial velocity is