What factors affect the amount of friction between objects?

The amount of friction between objects is primarily influenced by the interactions at the surfaces in contact. The correct answer highlights the role of the force of gravity, which affects the normal force acting on the surfaces, and the roughness of the contact surfaces, which determines how interlocking the surfaces are.

When two surfaces are pressed together, the normal force — which is impacted by gravity — increases the frictional force. Rougher surfaces tend to have more microscopic irregularities that increase the contact area and interlock more with one another, leading to higher friction. Thus, both gravity and surface roughness are crucial factors in determining friction.

Other factors, such as surface texture and temperature, can influence friction as well, but in this context, the combination of the force of gravity and roughness of the contact surfaces provides the most comprehensive understanding of friction’s mechanics.