Created by Isaac Newton:
First Law: An object at rest/in motion tend to remain at rest/in motion unless acted upon by an external force.
Second Law: F=MA (Pretty simple, Huh?)
Third Law: Every action has an equal and opposite reaction.

The Second Law is shortened to

ΣF = m • a

from

ΣF • t = mv₀ - mv

where v = velocity, m = mass, F = force, t = time.

because the mass of an object is constant and

(v - v₀) ÷ t = a

where a = acceleration.