Quote
By Isaac Newton
To every Action there is always opposed an equal Reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
- Source
- The Mathematical Principles of Natural Philosophy, translated by Andrew Motte, vol. 1, 1729 · Axioms or Laws of Motion, Law III, p. 20
- Read at
- Internet Archive (scan of the 1729 Motte edition, London: Benjamin Motte)
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Newton's Third Law of Motion, from the Principia (1687), in Andrew Motte's English translation of 1729 (The Mathematical Principles of Natural Philosophy, London: Benjamin Motte). The popular wording "equal and opposite reaction" is not Newton's.