Is there a quick way to find if a situation is an example of Newtons 1st, 2nd, or 3rd law?

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bandmanjoe | Middle School Teacher | (Level 2) Senior Educator

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Well, you're asking a lot here, to boil the great findings of Sir Isaac Newton down to a quick "Cliff Notes" version, but here goes!

The first law of motion is also called the law of inertia.  It basically says things at rest want to stay at rest and things in motion want to stay in motion.  If you have a question asking about changes in motion, it's Newton's first law, probably.  Or, if it mentions the dreaded "i" word, inertia, which is an object's tendency to resist changes in motion, it's Newtons first law.

The second law of motion is concerned with the generation of force as a direct interaction between an object's mass and acceleration.  The formula for this is Force = mass x acceleration.  If the question is asking about the force generated by an object which has "this much mass" and "this much acceleration", it's probably Newton's 2nd law.

The easiest one is the third law, which is the one everyone remembers:  "For every action force, there is an equal and opposite reaction force."  If it is a question about a force acting on something, and they want to know if the something acted back with an equal force, it is most definitely Newton's third law.

Hard to get it much shorter, but there it is:  Newton's 3 laws of motion, "Cliff Notes" version!


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