Whilst kinematics deals with the motion and deformation of a body, kinetics studies the forces that produce motion. The two types of forces are:
- Body forces (per unit mass or volume) are non-contact forces that act on the total mass of a continuum. Examples include gravitational force, electromagnetic force and inertial force.
- Surface forces (per unit area) are contact forces that act across an internal or external surface of a body. Examples include pressure, contact forces and frictional forces.
Figure. Magnetic (non-contact) vs. frictional (contact) forces. Images adapted from Newtown High School and Joey's Blog.
