A gun fires $N$ bullets per second, each of mass $m$ with velocity $v$. The force exerted by the bullets on the gun is

A force-time graph for a linear motion of a body is shown in figure. The change in linear momentum between $0$ and $7\mathrm{s}$ is

Consider the following two statements :

I. Linear momentum of a system of particles is zero

II. Kinetic energy of a system of particles is zero.

Two blocks of mass $m$ and $2m$ are connected by a light string passing over a frictionless pulley. As shown in the Fig. $7.67$, the mass $m$ is placed on a smooth inclined plane of inclination $30°$ and $2m$ hangs vertically. If the system is released, the block moves with an acceleration equal to: