# How can Newton's first law be derived from Newton's second law?

May 31, 2018

See below

#### Explanation:

"If" the 2nd Law is true:

• $\sum \boldsymbol{F} = m \boldsymbol{a}$

To help out the 1st Law:

• $\sum \boldsymbol{F} = \boldsymbol{0} \implies \boldsymbol{a} = \boldsymbol{0}$

That's the 1st Law :)

But needs some context, IMHO.

IMHO, Newton's 3rd Law is the Jewel in the Crown. Newton's 1st Law - you can convince yourself that it is redundant - it clearly signalled the end of the Aristotleiean viewpoint. The 2nd law seems so obvious, but maybe that is because it is (rightly) brainwashed into everyone at a very early stage.

Conservation of momentum is a (IMHO weird) truth of the Universe.