Which term refers to the force between an object and the surface it is moving over?

• A. Gravity
• B. Mass
• C. Friction
• D. Collision

Answer: (C)

Friction is the force that resists motion between surfaces in contact. It acts parallel to the surface and opposite to the direction of movement, so as an object slides or tries to slide, friction slows it down. This resistive force depends on how hard the surfaces press together (the normal force) and how rough the surfaces are, often summarized by F_friction = μ F_n. On a horizontal surface, the normal force is about the object's weight, so heavier objects can experience more friction, but friction itself is the resisting force, not the weight or mass.

Gravity is the downward pull toward Earth, not the resistance to sliding along a surface. Mass is the amount of matter in the object, which influences how much friction can arise but is not the frictional force itself. A collision is a brief, momentary impact between objects, not the ongoing force that opposes motion along a surface.