Normal force

The contact force exerted by a surface on an object, directed perpendicular to the surface at the point of contact. Its magnitude depends on the interaction and constraints, not necessarily on the object's weight.

Newton's laws of motion: Three laws relating an object's motion to the forces acting on it. The normal force is one term in the net force that determines acceleration.
Contact force: A force arising from physical interaction between bodies in contact. The normal force is the perpendicular component of a contact interaction.
Gravitational force: The attractive force between masses, described near Earth by an object's weight. Unlike gravity, the normal force comes from contact and need not point upward.
Scale: An instrument that measures force or infers mass from an object's support force. A scale typically senses the normal force exerted on its platform.
Contact mechanics: The study of forces, deformation, and motion where solid bodies touch. Surface deformation at contact produces the normal force.
Friction: A tangential contact force that resists relative motion or its tendency between surfaces. Friction acts parallel to the same contact interface where the normal force acts perpendicularly.
Tension: A pulling force transmitted through a stretched string, rope, cable, or similar connector. Tension can support an object without a surface pressing on it.
Elevator: A powered platform that transports people or goods between levels in a building. Acceleration changes the floor's normal force on a passenger and therefore the apparent weight.
Free-body diagram: A diagram showing an object and the external forces acting on it. It represents the normal force as an arrow perpendicular to the contact surface.
Weight: The gravitational force exerted on an object by a nearby astronomical body. Weight is often balanced by the normal force, but the two are distinct forces.

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