Newton’s Laws of Motion

1. Object in motion stays in motion unless acted upon by an external force. Inertia.
2. $F=ma$
3. Every action has an equal and opposite reaction. $F_{AB}=-F_{BA}$

Forces

A push or a pull, vector quantities measured in Newtons (N). The $F_{net}$ is the sum of all forces.

Friction

Kinetic friction: Friction that object feels when moving, where $F_{fr}={\mu }_k{F}_N$ For objects at rest, there is static friction, where $F_{fr}<{\mu }_s{F}_N$ . Note: ${\mu }_s>{\mu }_k$