<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (November 2010) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (November 2010) (Learn how and when to remove this template message) </Td> </Tr> <P> As described by the third of Newton's laws of motion of classical mechanics, all forces occur in pairs such that if one object exerts a force on another object, then the second object exerts an equal and opposite reaction force on the first . The third law is also more generally stated as: "To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts ." The attribution of which of the two forces is the action and which is the reaction is arbitrary . Either of the two can be considered the action, while the other is its associated reaction . </P> <P> When something is exerting force on the ground, the ground will push back with equal force in the opposite direction . In certain fields of applied physics, such as biomechanics, this force by the ground is called' ground reaction force'; the force by the object on the ground is viewed as the' action' . </P>

Who said to every action there is a reaction
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