An inextensible string passing over a smooth pulley connects two blocks of masses $m_1$ and $m_2$ ($m_2 > m_1$) vertically. If the acceleration of the system is $\left(\dfrac{g}{n}\right)$, then the ratio of masses $\left(\dfrac{m_2}{m_1}\right)$ is

A block of mass M is lying on a horizontal frictionless surface. One end of the uniform rope of half the mass of the block is fixed to the block which is pulled in the horizontal direction by applying a force F at the other end. The tension in the middle of the rope will be

A machine gun fires a bullet of mass 40g with a speed of $600 \text{ ms}^{-1}$. The person holding the gun can bare maximum force of 168N on it. The number of bullets that can be fired from the gun per second is

$100$ balls each of mass $m$ moving with speed $v$ simultaneously strike a wall normally and reflected back with same speed, in time $t$ s. The total magnitude of force exerted by the balls on the wall is