Newton's Third Law Scenarios — Click to explore
🏃 Person Pushing Wall
Person pushes wall with force F. Wall pushes back on person with equal force −F. The person accelerates backward (if on frictionless floor), the wall doesn't move (attached to Earth).
Action (on wall)
→ F = 50 N
Reaction (on person)
← F = 50 N
F_person→wall = −F_wall→person = 50 N
🍎 Book on Table
Book pushes table down with its weight (gravitational force = contact force here). Table pushes book up with normal force. These are an action-reaction pair of contact forces.
F_book→table = −F_table→book = 9.8 N (Normal force pair)
🚀 Rocket Propulsion
Rocket pushes exhaust gas downward. Gas pushes rocket upward with equal force (thrust). This is how rockets work in the vacuum of space — no air needed to "push against"!
F_rocket→gas = −F_gas→rocket = 3.5 × 10⁶ N (Thrust)
🌍 Earth-Moon Gravity
Earth pulls Moon toward it (gravity). Moon pulls Earth toward it with exactly the same force. Earth barely moves because M_Earth >> M_Moon.
Earth on Moon
← 1.98×10²⁰ N
Moon on Earth
→ 1.98×10²⁰ N
F = Gm₁m₂/r² (gravitational pair, same magnitude)
🏊 Swimming
Swimmer pushes water backward. Water pushes swimmer forward. The swimmer accelerates because the net force on the swimmer is forward (reaction from water minus drag).
F_swimmer→water = −F_water→swimmer (contact force pair)