Newton's 3rd Law Discussed Learning Goal: To understand Newton's 3rd law, vwhich states that a physical interaction always generates a pair of forces on the two interacting bodies • Part B In Principia, Newton wrote: 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 two forces in each pair act in opposite directions. (translation by Cajori) O true The phrase after the colon (often omitted from textbooks) makes it clear that this is a statement about the nature of force. The central idea is that physical interactions (eg. due to gravity, bodies touching, or electric forces) cause forces to arise between pairs of bodies. Each painvise interaction produces a pair of opposite forces, one acting on each body. In summary, each physical interaction between two bodies generates a pair of forces. Whatever the physical cause of the interaction, the force on body A from body B is equal in magnitude and opposite in direction to the force on body B from body A O false Submit Request Answer Incidentally, Newton states that the word "action" denotes both (a) the force due to an interaction and (b) the changes in momentum that it imparts to the two interacting bodies. If you haven't leamed about momentum, don't worry, for now this is just a statement about the origin of forces. • Part C Mark each of the following statements as true or false. If a statement refers to "hvo bodies" interacting via some force, you are not to assume that these two bodies have the same mass. The two forces in each pair can either both act on the same body or they can act on different bodies. O true O false Submit Reguest Answer • Part D The two forces in each pair may have different physical origins (for instance, one of the forces could be due to gravity, and its pair force could be due to friction or electric charge). O true O false Submit BesutstAnswer Part E The two forces of a 3ed law pair always act on different bodies. O true O false Submit Reguest Answer • Part F Given that two bodies interact via some force, the accelerations of these two bodies have the same magnitude but opposite directions. (Assume no other forces act on either body.) > View Available Hintts) O true O false Submit • Part G According to Newton's 3rd law, the force on the (smaller) moon due to the (larger) earth is O greater in magnitude and antiparallel to the force on the earth due to the moon. O greater in magnitude and parallel to the force on the earth due to the moon. O equal in magnitude but antiparallel to the force on the earth due to the moon O equal in magnitude and parallel to the force on the earth due to the moon. O smaller in magnitude and antiparalel to the force on the earth due to the moon. O smaller in magnitude and parallel to the force on the earth due to the moon.