Question

Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play:

A) only if the objects are solid
B) only if one of the two objects is liquid
C) only if one of the two objects is gaseous
D) irrespective of whether the objects are solids, liquids, or gases

Answer 1

Frictional forces occur irrespective of whether the objects in contact are solid, liquid, or gaseous, and are caused by both surface roughness and molecular adhesive forces.

Step-by-step explanation:

The student has asked which conditions induce the force of friction between surfaces. The correct answer is D) irrespective of whether the objects are solids, liquids, or gases. Frictional forces, such as f, always oppose motion or attempted motion between surfaces in contact. This is due to both the roughness of the surfaces and the adhesive forces between the molecules that make up the objects. Whether the surfaces in question are solid, liquid, or gaseous, friction can still occur as long as there is an interaction at the molecular level. When discussing solids, such as rubber-soled shoes compared to leather soles, the difference in friction levels can be attributed to the varying adhesive forces based on the material composition.