Force is an influence that
affects the (inertia or) motion of a body or its state of rest. It is
like a push or pull.
It makes a body with mass to alter its state of
rest (inertia) or of uniform motion in a direction. A force acts on a
body through a contact or through a field in space.
Forces are of two broad categories:
1. Contact forces:
These forces are exerted by one object
on another object through the surface of contact between them. The force could be at any angle to the contact
Examples are: Friction
force, Normal (reaction) force, Tension in a string or rod, Spring (restoration against extension or
compression) force, an applied force (push or pull), Air resistance or drag,
Buoyancy force in a fluid.
2. Distant forces or non-contact forces:
These are the forces acting on an
object though space. There is no contact between the body causing the force and
body on which the force acts. The force
is caused due to the field of force in space caused by gravity or an electric
charge or a magnetic pole.
Examples are: Electric force of
attraction, Nuclear forces (weak forces), Magnetic force of attraction or repulsion, Gravitational
force of attraction.