Newton's law of inertia

a reference to the three laws of motion and interaction formulated by Sir Isaac Newton (1642-1727), English scientist and mathematician. These laws are intended to describe how all moving bodies on the earth react:

1. a body at rest remains at rest and a body in motion remains in motion unless acted on by an external force;
2. the motion of a body changes in proportion to the size of the force applied to it;
3. every action produces an equal but opposite reaction.