When a gun is fired, the persons firing the gunreceives a 'kick' from the gun. The gun recoils from the shot. Themarksman is well advised to brace themselves for this kick.
A typical bullet has a mass of 20 grams and travels ataround 500 metres per second.
A typical gun has a mass of 1.5 kilograms or so.
Suppose the gun is fired. Before firing man and gun arestationary, so the net momentum is zero.
The principle of conservation of momentum means thatafter the gun is fired, the momentum will be zero too.
This means
sothat
With the numbers given above, the recoil velocity ofthe gun is