The third law states that all forces between two objects exist in equal magnitude and opposite direction: if one object A exerts a force F on a second object B, then B simultaneously exerts a force F on A, and the two forces are equal in magnitude and opposite in direction: F = − F. The third law means that all forces are interactions between different bodies, or different regions within one body, and thus that there is no such thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by Body A on Body B is called the "action '', and the force exerted by Body B on Body A is called the "reaction ''. This law is sometimes referred to as the action - reaction law, with F called the "action '' and F the "reaction ''. In other situations the magnitude and directions of the forces are determined jointly by both bodies and it is n't necessary to identify one force as the "action '' and the other as the "reaction ''. The action and the reaction are simultaneous, and it does not matter which is called the action and which is called reaction; both forces are part of a single interaction, and neither force exists without the other.
the law that states that for every action
action - reaction law