Question

How does the roughness of surfaces that are touching affect the friction between the surfaces?

Answer 1

Hint: Frictional force is a force that opposes the relative motion between the surfaces that are touching. Friction can be both a boon and a bane i.e., work for or against us, like putting sand on an oil spill increases friction so you are less likely to slip. Contrary to this, too much friction between moving parts in a machine can cause the machine parts to wear out.

Complete step by step answer:
Frictional force or frictional resistance is directly proportional to the force that is applied to the two surfaces. It also depends upon the roughness of the surfaces. The rougher the surfaces, the greater the resistance. The friction comes into the picture when two surfaces move against each other in opposite directions. The resistance offered by friction depends directly on the force applied for the relative motion between the surfaces. It is always calculated as vertical or normal force and it also depends on the roughness of the surfaces, it is represented as the coefficient of friction (\[\mu \]). Lower the value of $\mu $, smoother the surfaces and the lesser will be the resistance; more the value of $\mu $, rougher the surface and thus more the resistance.

Note:
• The friction between the two surfaces depends upon the surface quality like a smooth surface will offer lesser resistance as compared to the rough surface.
• Rough surface means more irregularities, more irregularities mean more power to overcome those irregularities means more friction to oven come.