Which statement about friction on rough surfaces?

• A. Weight
• B. Surface roughness
• C. Temperature
• D. Wetness

Answer: (B)

Friction on rough surfaces is mainly about how the tiny bumps and irregularities on the surfaces interact when you try to slide them past each other. Rough surfaces have many asperities that interlock and catch on one another. When you push, those interlocked peaks must shear, deform, and slide over each other, which wastes energy and requires a larger force to keep things moving. That’s why roughness tends to increase friction compared with smooth surfaces.

Other factors like weight, temperature, or wetness can affect friction in different ways, but they are not describing what happens specifically because the surface is rough. Weight changes the normal force pushing surfaces together; temperature and wetness can alter material behavior or add lubrication, but the defining feature of friction on rough surfaces is the roughness itself and the interlocking of surface features.