Newton's Third Law
3 guided lessons · 27 checks · 1. Forces & Motion → Momentum
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What is Newton's third law?
Every push or pull is one half of a deal: when object A acts on object B, object B acts back on A. Newton's third law states that the two forces are equal in size and opposite in direction. This lesson builds the statement, tests it on walking, and separates it from the laws describing single objects.
What you know already
The Momentum lessons have already shown you what momentum is, how collisions conserve it, and how F = ma ties force to changing motion. One question remains: when two bodies interact, how do the forces they feel compare? Newton's third law answers with one symmetric statement about interacting objects, and this note also trains you to tell true third law pairs apart from merely balanced forces.
Key points of understanding
- Newton's third law describes the forces that appear when two different objects interact with each other.
- Newton's first and second laws instead cover forces acting on just one object.
- When any two objects interact, each exerts on the other a force equal in size and opposite in direction.
- Walking works because your foot pushes backwards on the ground while the ground pushes forwards on your foot.
- The two interacting objects here are the foot and the ground, pushing on each other with equal strength.
The foot pushes the ground backwards, and the ground pushes the foot forwards. Newton's third law explains the forces that enable people to walk
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1.What is Newton's third law?
Every push or pull is one half of a deal: when object A acts on object B, object B acts back on A. Newton's third law states that the two forces are equal in size and opposite in direction. This lesson builds the statement, tests it on walking, and separates it from the laws describing single objects.
The foot pushes the ground backwards, and the ground pushes the foot forwards. Newton's third law explains the forces that enable people to walk
Key points
- Newton's third law describes the forces that appear when two different objects interact with each other.
- Newton's first and second laws instead cover forces acting on just one object.
- When any two objects interact, each exerts on the other a force equal in size and opposite in direction.
Guided content from the SME authoring corpus — note rn_8wqvPtsCCh3gdJN5, pinned at 0cea83a78102 · promoted SyllabAI/syllabai-resources b3caaaa90c5e
