Which force slows down a sliding object moving on a surface?

• A. Air Resistance
• B. Mass
• C. Sliding friction
• D. Velocity

Answer: (C)

When an object slides across a surface, the force that slows it down is sliding friction between the two surfaces. This friction acts opposite to the direction of motion, converting some of the object's kinetic energy into heat as the surfaces rub past each other. The amount of sliding friction depends on how rough the surfaces are and how hard the object pushes into the surface (the normal force). Mass isn’t a force, and velocity is a measure of speed, not a force that slows motion. Air resistance can slow objects moving through air, but the main braking force for something sliding on a surface is the friction between the object and the surface.