Definition of Force

 From Newton’s first law of motion, we have that an object will forever remain where it is kept unless a force is applied to move it; and also that an object will continue to move along a straight line forever at uniform speed unless a force is acted on it to change its speed and direction. 

Therefore, we can define force as:

An agent which changes a body’s state of rest or uniform motion along a straight line.

Force can broadly be divided into two groups, namely Contact forces and force field.

Contact Forces: These are forces that make contact with the bodies they impact. They include such forces as forces of pull and push, tension, friction, and reaction.

Force Field: Unlike contact forces, force fields do not make contact with the bodies they affect. They impact bodies from a distance within their fields. Examples include gravitational forces, electrical forces, and magnetic forces.

Force is a vector quantity. This means that it has both magnitude and direction. In physics, things which have both magnitude and direction are regarded as vector quantities.

Calculation of Force: the magnitude of force which acts on a body can be deduced by applying Newton’s second law of motion.

See calculation of force based on Newton’s second law of motion here.

Newton's First Law Of Motion