🔋college physics i – introduction review

Newton’s third law of motion

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that forces always come in pairs, acting on two interacting objects.

5 Must Know Facts For Your Next Test

  1. The law implies that forces are mutual and occur simultaneously.
  2. An example includes a swimmer pushing against water; the water pushes back with an equal force.
  3. Action-reaction forces act on different objects, not on the same object.
  4. The magnitude of both forces is always equal, but they are in opposite directions.
  5. This law is fundamental in understanding the conservation of momentum.

Review Questions

"Newton’s third law of motion" also found in: