Which force is the force that acts perpendicular to a surface to support an object resting on it?

• A. Friction
• B. Normal force
• C. Magnetic force
• D. Electrical force

Answer: (B)

Normal force is the support force that a surface exerts on an object at the point of contact. It acts perpendicular to the surface (the line normal to the surface) and pushes the object away from the surface, preventing it from sinking in. When nothing else pushes up or down, this force balances the object's weight, which is why you don’t accelerate downward while resting on a table. On an incline, the normal force is still perpendicular to the surface but is smaller in magnitude because gravity can be split into a perpendicular component that the normal force balances and a parallel component that would tend to slide the object down the plane. Friction acts along the surface and resists motion, while magnetic or electrical forces would only come into play if those fields or charges are involved, not as the usual support force for a resting object.