Law 1 (Law of Inertia):
An object will maintain its velocity AKA it will probably continue to do that UNLESS a nonzero force is acted upon it.
The HIGHER the mass the HIGHER the inertia, like a bowling bowl which is harder to stop, than a soccer ball.
Mass is the measure of inertia!

A frame of reference in which Newton’s First Law is valid.
A train where a guy only sees the train move, AKA it doesn’t suddenly stop or decelerate, etc.

Law 2 The definition of (net)Force / Newtons:
F = m*a
a = F/m
As the force makes the object accelerate/move

Translational Equilibrium:
When the net force is 0.
AKA at REST or constant VELOCITY

Force Unit:
Kg / s^2
This means 1 N is the force to move a 1 kg object 1 m/2
It is a VECTOR

External Force:
Something that acts upon an object, like pushing it

Internal Force:
Forces that act within the same system, and don’t contribute to any motion.

A McDonald’s quarter pounder is about 1N
OR one medium-size apple, like the one that hit Newton on the head.
AND a human is about 800 N

Law 3rd of Motion:
Whenever an object exerts a force, it will get the same force back.

The reason they don’t cancel out:
Each force is applied to different systems, so the force of a push is acted on one system, which is moved, and then the opposite force is acted on you, and moves you away.

Normal force:
Perpendicular to what you are moving.
This acts against a PUSHING FORCE.
AKA there is always a force that pulls in the opposite direction of the object, but it can be overcome, which is how things move.
It’s a variable force, as it provides “just enough” force to keep something from going through an object, but the force depends on the mass, so it can change with that if you like to put more stuff on top.