Newton's 3rd Law
Action Force & Reaction Force
For every action there is an equal and opposite reaction. In every interaction there is a pair of forces acting on the pair of interacting objects. These forces are the action force and the reaction force. The size of the force on the first object must equal the size of the force of the second object. The direction of the first object must be in the opposite direction of the second object.
For example: If the action force is a baseball player hitting a baseball with the bat the reaction force is the baseball reacting to the bat.
For example: If the action force is a baseball player hitting a baseball with the bat the reaction force is the baseball reacting to the bat.