Newton's Laws of Force.

First Newton's law

If an object experiences no net force, then its velocity is constant: the object is either at rest (if its velocity is zero), or it moves in a straight line with constant speed (if its velocity is nonzero).

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Second Newton's law

The acceleration a of a body is parallel and directly proportional to the net forceF acting on the body, is in the direction of the net force, and is inversely proportional to the mass m of the body:
F=ma, [N]
we can also describe it as
F=ma=m

dv

dt

F=

dp

dt

, where:
m - mass of the object
a - acceleration
v - velocity of the object
t - time

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Third Newton's law

When a first body exerts a force A on a second body, the second body simultaneously exerts a force B = −A on the first body. This means that A and Bare equal in magnitude and opposite in direction.