Newton's third law of motion pertains to forces between two objects. If you jump off a skateboard, Newton's third law of motion is applied because you applied a force to the skateboard and the skateboard applied an equal (in magnitude) and opposite (in direction) force on you. Forces always exist in pairs, newton's third law defines these action and reaction forces. If a force occurs, there are action reaction forces. Action reaction forces can cause changes in motion, are equal in strength but opposite in direction, and act on different objects. Newton's third law tells us that action reaction forces are equal and opposite, but does not mean that the effects of those force are equal. If we understand Newton's third law and momentum, we can predict how the motion of colliding objects will change. Momentum is the result of the mass of the object times the object's velocity. Momentum is conserved during an interaction as long as the objects are not affected by outside forces. this means that the total momentum of objects prior to hitting each other will equal the total momentum of the objects after the interaction. Finally there is a Lab on Newton's third law and momentum, about 2 car COLLISION SIMULATOR.