Any body keeps its resting position or uniform rectilinear motion as long as no force acts on them.
Force is the physical vector size by which a body acts on another body, transmitting the mechanical movement
Newton found that a force acting on a body imparts to it an acceleration proportional to force and inversely proportional to the mass of the body:
(principle of force or second law of dynamics)
When a body acts on another body with a force (called force of action), the second body also acts on the first one with a force (called reaction force) of the same size and direction, but of the opposite direction. This principle is also known as the principle of action and reaction.
Principle 4 (Overlapping Principle)
If several forces act at the same time on a body, each force produces its own acceleration independently of the presence of the other forces, the resulting acceleration being the vector sum of the individual accelerations.