Which force is the contact force that acts perpendicular to the surface to support objects at rest on a surface?

Which force is the contact force that acts perpendicular to the surface to support objects at rest on a surface?

• A. Normal force
• B. Friction
• C. Gravitational force
• D. Applied force

Answer: (A)

The normal force is the contact force that acts perpendicular to the surface and pushes the object away from the surface to support it at rest. It arises from the surface pushing back when something sits on it, preventing the object from sinking into or penetrating the surface. For an object at rest on a horizontal surface, the normal force balances the part of gravity pressing into the surface, so the perpendicular component of motion is zero. On an incline, the normal force remains perpendicular to the surface (often N = mg cos θ), while gravity also has a parallel component that would cause sliding unless balanced by friction. Friction acts along the surface and opposes motion, gravity is downward, and an applied force is any external force applied to the object. The perpendicular, supporting contact force is the normal force.

The normal force is the contact force that acts perpendicular to the surface and pushes the object away from the surface to support it at rest. It arises from the surface pushing back when something sits on it, preventing the object from sinking into or penetrating the surface. For an object at rest on a horizontal surface, the normal force balances the part of gravity pressing into the surface, so the perpendicular component of motion is zero. On an incline, the normal force remains perpendicular to the surface (often N = mg cos θ), while gravity also has a parallel component that would cause sliding unless balanced by friction. Friction acts along the surface and opposes motion, gravity is downward, and an applied force is any external force applied to the object. The perpendicular, supporting contact force is the normal force.