Question

A bullet of mass $40g$ is fired from a gun of mass $10kg$. If velocity of bullet is $400m/s$, then the recoil velocity of the gun will be

• A. $1.6m/s$ in the direction of the bullet
• B. $1.6m/s$ opposite to the direction of the bullet
• C. $1.8m/s$ in the direction of the bullet
• D. $1.8m/s$ opposite to the direction of the bullet

Answer 1

The correct option is B $1.6m/s$ opposite to the direction of the bullet

Let velocity of gun is $v$.

There is no external force acting, so linear momentum will conserve.

Before the firing, Linear Momentum $=0$

After the firing, Linear momentum $=0.04\times 400+10\times v$

$\Rightarrow 0.04\times 400+10\times v=0$ $\Rightarrow v=-1.6m/s$

Hence, $1.6m/s$ opposite to the direction of the bullet.