A block of mass $10 \mathrm{kg}$ is hanging over a smooth and light pulley through a light string and the other end of the string is pulled down by a constant force $F$. The kinetic energy of the block increases by $20 \mathrm{J}$ in $1 \mathrm{s}$

Two particles $A$ and $B$ of masses $2 \mathrm{kg}$ and $3 \mathrm{kg}$ moving on a smooth horizontal surface with speed $1.5 \mathrm{m} {\mathrm{s}}^{-1}$ and $2 \mathrm{m} {\mathrm{s}}^{-1}$collide perfectly inelastically, then

A particle strikes a smooth horizontal surface at an angle $\theta >0$ and it rebounds at an angle $\varphi$ as shown