THE THIRD LAW
If object 1 exerts a force on object 2, then object 2 exerts a force back on
object 1, equal in strength but in the opposite direction.Newton’s third law was originally stated in the form, “For every action, there is an
equal and opposite reaction.” Because of this historical phrasing, these two forces,
F1-on-2 and F2-on-1, are called an action/reaction pair.
The Skinny on the Third Law
Two objects must interact for a force to exist. When both objects interact,
each body experiences a force due to the other interacting body. If A and
B are the two interacting masses, let F 1 be the force acting on A due to B;
F 2 is the force acting on B due to A. F 1 and F 2 are the same magnitude
but have opposite directions. F 1 = −F 2.