To every action there is an equal and opposite reaction In other words, if two objects interact, then the force exerted by object 1 on object 2 is equal in magnitude and opposite in direction to the force exerted by object 2 on object 1. Thus, an isolated force cannot exist in nature. This law has already been mentioned with reference to the force with a table exerts on a book placed upon it and also in connection with the weight o a body in an accelerating elevator ( see post : Newton' second law of motion.... ). We shall now discuss another aspect of the law. When a bullet is fired from a gun equal and opposite forces are exerted on the bullet and the gun during the time the bullet is passing down the barrel.Since,therefore,both bullet and gun are acted upon by equal forces for the same time, they will, in accordance with the second law of motion, acquire equal and opposite momemta. The backward momentu...