Newton's laws of motion

Newton's laws of motion describe the relationship between the forces acting on a body and the motion they produce.

The first law, the law of inertia, states that a body remains in the state of rest or in uniform motion in a straight line unless it is acted on by an external force.

The second law states that the rate of change of velocity-that is, the acceleration (a)-- produced by a force is proportional to that force (F) and inversely proportional to the mass (m) of the body:

a = F/m or F = ma.

The third law states that to every action there is an equal and opposite reaction