Physics: Forces and Energy - Contact and Non-contact Forces

A force is a push or pull upon an object resulting from the object's interaction with another object. Forces are vector quantities, meaning they have both magnitude and direction, measured in Newtons ($N$).

Contact Forces occur when two objects are physically touching. Examples include Friction ($F_f$), Air Resistance ($F_{drag}$), Tension ($T$), and Normal Reaction Force ($F_N$).

Non-contact Forces act over a distance through a field, without physical contact. Examples include Gravitational Force ($W$), Electrostatic Force, and Magnetic Force.

Mass ($m$) is a measure of the amount of matter in an object, measured in kilograms ($kg$). It remains constant regardless of location.

Weight ($W$) is the force of gravity acting on an object's mass. It changes depending on the gravitational field strength ($g$), measured in Newtons ($N$).

Normal Reaction Force ($F_N$) is the support force exerted upon an object that is in contact with another stable object, acting perpendicular to the surface.

Resultant (Net) Force ($F_{net}$) is the single force that represents the combined effect of all forces acting on an object.