An object will remain at rest or in uniform motion unless acted upon by an external force.
Also known as the Law of Inertia. This means objects naturally resist changes to their motion.
F = ma (Force = Mass × Acceleration)
The acceleration of an object depends on the net force acting upon it and its mass.
For every action, there is an equal and opposite reaction.
When two bodies interact, they apply forces to each other that are equal in magnitude and opposite in direction.