Forces and Interactions A force is not a thing in itself but makes up an interaction between one thing and another. These forces are equal in magnitude and opposite in direction and comprise a single interaction.
Example of the Boxer •The boxer’s fist can only exert as much force on the tissue paper as the tissue paper can exert on the fist. • The fist can’t exert any force at all unless what is being hit exerts the same amount of force back. • An interaction requires a pair of forces acting on two objects.
Example of the Boxer He can hit the massive bag with considerable force. But with the same punch he can exert only a tiny force on the tissue paper in midair.
Which Exerts the Force and Which Receives the Force? Isaac Newton’s answer:–Neither force has to be identified as “exerter” or “receiver”.–Both objects must be treated equally. (Think about the wall and person.)
Newton’s Third Law of MotionNewton’s third law states:–Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.
Newton’s Third Law of MotionFaction= Freaction (ma=ma) •i. One force is called the action force •ii. The other force is called the reaction force
Easy way to remember Newton’s 3rdLaw of Motion •“For every action there is always an equal and opposite reaction.”