Newton's third law
Interaction forces act on different bodies in equal and opposite pairs.
Key knowledge
In the Newtonian interaction model, the force exerted by A on B equals the negative of the force exerted by B on A. These forces act on different bodies, so they do not cancel in the force balance for either body alone.
Values and equations
F_A→B = −F_B→A
- F_A→B
- Force vector exerted by A on B N
- F_B→A
- Force vector exerted by B on A N
Conditions and scope
- Compare the paired forces of the same interaction, in the same inertial frame.
- This particle-only Newtonian pairing is not a complete account of momentum carried by electromagnetic fields.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
OpenStax 5.5: interaction pair and separate-body force balances; NASA: equal/opposite forces on distinct objects.
2026-10-10 · Newtonian paired-force statement only; contact force and weight on the same body need not be a third-law pair.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
In the stated Newtonian interaction model, paired forces are equal, opposite and act on different bodies.
They do not cancel in a force balance for only one of those bodies.
Siyavula
- Newton’s laws · Physical Sciences 11 South AfricaEnglish
Newton’s third law, ESBKV
- Newton’s laws · Physical Sciences 11
Entry details
Permanent link to this entry ↗- Record identity
- physics-newtons-third-law
- Revision
- core.1
- Structured reference record
- Essential core · first collection · University core expansion