<P> 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 . </P>
<P> 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 . </P>
the law that states that for every action
the law that states that for every action
action - reaction law
action - reaction law