Newton's Third Law of Motion

If an object A exerts a force on object B, then object B must exert a force of equal magnitude and opposite direction back on object A.

$$F_{AB}=-F_{BA}$$

($F_{AB}:$ force on A cuz of B)

• Such pairs are called third law force pairs.
  • Their are other force pairs with equal magnitude and opposite direction.
  • Like Normal force from a table and the gravity of earth. This is not a third law force pair. N is between table and ball, and gravity is between earth and ball.
  • But a ball kept on the earth directly will experience the third law pair force. Normal from earth and gravity from earth.