Normal contact force

A normal contact force is the supporting push exerted by a surface. It acts perpendicular to the surface: ‘normal’ means at right angles here. A horizontal desk pushes upwards on a laptop resting on it.

A book resting on a table experiences an upward normal contact force from the table. ‘Normal’ means perpendicular to the surface, so the normal force from a sloping surface is not vertically upward. Friction acts along the surfaces in contact and opposes their relative movement, or their tendency to slide.