Newton's First Law

BHS -> Mr. Stanbrough -> Physics -> Mechanics -> Newton's Laws -> Newton's First Law -> this page

When I was still pretty young - I don't know how old exactly - I had a ball in a wagon I was pulling, and I noticed something, so I ran up to my father to say that, "When I pull the wagon, the ball runs to the back, and when I am running with the wagon and stop, the ball runs to the front. Why?

He said, "That nobody knows." He said, "It's very general, though, it happens all the time to anything; anything that is moving tends to keep moving; anything standing still tries to maintain that condition. If you look close you will see the ball does not run to the back of the wagon where you start from standing still. It moves forward a bit too, but not as fast as the wagon. The back of the wagon catches up with the ball which has trouble getting started moving. It's called inertia, that principle."

I did run back to check, and sure enough the ball didn't go backwards. He put the difference between what we know and what we call it very distinctly.

Richard Feynman - from his lecture on "What is Science?" given to the NSTA, Physics Teacher Vol. 7, issue 6, 1968, pp. 313-320.

 

Aristotle (wrong)	Newton (right)
Forces cause velocities	Forces change velocities

---

Newton's First Law

Newton's First Law is a very powerful and simple principle - which is often misunderstood and mis-applied. There are many ways to think about the First Law, so you should read and ponder "How many ways can you state Newton's First Law?" - the more ways you can approach Newton's First Law, the more likely you are to really understand it.

Many of the misconceptions relating to Newton's First Law concern a misunderstanding of the concept of force, so please read "Thoughts on force...".

Applying Newton's First Law correctly makes many apparently difficult and strange situations into really easy and straightforward situations. Many of these situations are common, everyday occurrences - for example, see Riding in a Car.

---