Mechanics · Forces & Newton's laws
Chapter 1 · 3
The idea
Newton's laws and F = ma
Newton's three laws and the one equation that runs all of dynamics — the RESULTANT force equals mass times acceleration — applied along a line and to forces given as 2-D vectors, why weight is mg and the normal reaction is whatever balances the rest, and how a lift problem is just F = ma done vertically.
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Mechanics · Forces & Newton's laws
Newton's laws and F = ma
Newton's three laws and the one equation that runs all of dynamics — the RESULTANT force equals mass times acceleration — applied along a line and to forces given as 2-D vectors, why weight is mg and the normal reaction is whatever balances the rest, and how a lift problem is just F = ma done vertically.
Why it works
Three laws
- Newton's first law. A body stays at rest or moves with constant velocity unless a resultant force acts. So constant velocity needs no net force — the forces are balanced. A car cruising at a steady has its driving force exactly cancelled by resistance.
- Newton's second law. A resultant force makes a body accelerate, in the same direction, with This is the workhorse. The force in it is the resultant of all forces, never just one of them.
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