I'm trying to better my understanding of Newton's second law.
Who created the concepts of force, mass and acceleration, and how did Newton discover that force, mass and acceleration are proportional to each other?
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$\begingroup$ Are you asking for the entire history of how forces were discovered ? $\endgroup$– ACRafiCommented Oct 8, 2021 at 6:41
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$\begingroup$ Lol no, unless you think that would be helpful. $\endgroup$– watchyCommented Oct 8, 2021 at 6:46
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$\begingroup$ He saw an apple falling $\endgroup$– user65081Commented Oct 8, 2021 at 6:52
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1$\begingroup$ @watchy arthurstinner.com/stinner/pdfs/1994-storyofforce.pdf $\endgroup$– MechanicCommented Oct 8, 2021 at 7:52
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4$\begingroup$ This question is more suitable for History of Science and Mathematics $\endgroup$– Kris WalkerCommented Oct 8, 2021 at 9:33
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1 Answer
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How did Newton discover that force, mass and acceleration are proportional to each other?
Newton introduces his three laws of motion in the very first part of the Principia, titled Axioms, or Laws of Motion. In the Scholium or discussion section that follows, he describes in some detail the experimental evidence that led him to formulate these laws. At the beginning of the Scholium he says
I have laid down such principles as have been received by mathematicians, and are confirmed by abundance of experiments.
He start5s by describing Galileo's experiments with falling bodies and balls rolling down planes, which led Galileo to propose that falling bodies have a uniform acceleration. Although Newton does not actually use the term acceleration, he says the same thing in a more long-winded way:
When a body is falling, the uniform force of its gravity acting equally, impresses, in equal particles of time, equal forces upon that body, and therefore generates equal velocities; and in the whole time impresses a whole force, and generates a whole velocity proportional to the time.
Newton then describes the "experiment of pendulums" carried out by himself, Christopher Wren and other members of the Royal Society. In these experiments an object suspended by a string is released and collides with another suspended object. The velocities of the first object immediately before the collision can be determined from the height at which it is released, and the velocities immediately after collision can be determined from the height which the objects reach after rebounding. These experiments led Newton to formulate the principle of conservation of momentum, which he states as a corollary to his three axioms. Newton concludes his description of the pendulum experiments by saying:
And thus the third Law, as far as it regards percussion and reflexions, is proved by a theory exactly agreeing with experience.
answered Oct 8, 2021 at 10:46