A man holding a rifle (mass of person and rifle together is $100 \mathrm{kg}$) stands on a smooth surface and fires $10$ shots horizontally in $5 \sec$. Each bullet has a mass $10 \mathrm{g}$ with a muzzle velocity of $800 \mathrm{m} {\mathrm{s}}^{-1}.$ The velocity which the rifle man attains after firing $10$ shots will be

A solid cylinder of mass $m$ and radius $R$ rolls down inclined plane without slipping. The speed of its $C.M.$ when it reaches the bottom is___

A planet revolves in an elliptical orbit around the sun. The semi-major and semi-minor axes are $a$ and $b$. Then, the square of time period $T$ is directly proportional to-

A block of mass $5 \mathrm{kg}$ resting on a horizontal surface is connected by a cord, passing over a light frictionless pulley to a hanging block of mass $5 \mathrm{kg}$. The coefficient of kinetic friction between the block and the surface is $0.5$. Tension in the cord is $\left(g=9.8 \mathrm{m} {\mathrm{s}}^{-2}\right)$