Newton's third law of motion - Forces

Notes:

In this lesson, we will learn:

• Newton's third law of motion
• Explaining physical phenomena using Newton's third law
• Calculations with Newton's second and third laws

Notes:

• Newton's third law: when one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
  • Also stated: "for every action, there is an equal and opposite reaction."
• Each force in action-reaction force pair is located on a different object in the pair. Each force in action-reaction force pair also has the same "type."
  • Example: if a wooden block slides across a floor, the floor exerts a force of friction on the block and the block exerts a force of friction that is equal in magnitude but opposite in direction on the floor. The forces in this pair are on different objects (one acts on the block, and the other acts on the floor), and both are the same type of force (friction).

Newton's Third Law

For object A exerting a force on object B:

$\vec{F}_{A on B} = - \vec{F}_{B on A}$

$\vec{F}_{A on B}:$ force A is exerting on B, in newtons (N)

$\vec{F}_{B on A}:$ force B is exerting on A, in newtons (N)