Final answer:
When a rifle is fired, according to Newton's third law of motion, the bullet being propelled forward causes the rifle to recoil or kick backward. This principle also applies to a recoilless rifle, where some of the gases escape out the back to reduce the recoil effect. Standing close behind a recoilless rifle when it is fired can still be dangerous.
Step-by-step explanation:
When a rifle is fired, the bullet is propelled forward with a certain amount of force. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. This means that when the bullet is pushed forward, an equal force is exerted in the opposite direction, causing the rifle to recoil or kick backward.
This principle also applies to a recoilless rifle, which has an open barrel at both ends. When the bullet is fired, the force pushing it out of the muzzle is accompanied by a force pushing the rifle backward. However, because the barrel is open at both ends, some of the gases escape out the back, reducing the backward force and minimizing the recoil effect.
Standing close behind a recoilless rifle when it is fired can still be dangerous, as some of the gases and debris can still come out the back and pose a risk to the person standing there. It is important to follow proper safety protocols and stand in a safe location when firearms are being discharged.