Question

How does force of friction depends on the area of contact of two surfaces?

  (a) directly proportional to the area
  (b) inversely proportional to the area
  (c) independent of the area
  (d) directly proportional to the square of the area ​

Answer 1

Answer:

ANSWER

(I). Frictional resistance is directly proportion to the force applied to the two surfaces as well as the roughness of the surfaces. The rougher the surfaces, the greater the resistance

Friction is caused when two surfaces move against each other in opposing directions.

The resistance offered by friction depends directly on the force applied to move the two surfaces and the roughness of the surfaces.

The smoother the surfaces, the less the resistance; the rougher the surface, the more the resistance

(II).The frictional force is directly proportional to the normal force between the two surfaces in contact. Because when two surfaces are pressed together harder, there is more friction.

(III). Since pressure equals force divided by the area of contact, it works out that the increase in friction generating area is exactly offset by the reduction in pressure; the resulting frictional forces then, are dependent only on the frictional coefficient of the materials and the force holding them together.

Answer 2

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The force due to friction is generally independent of the contact area between the two surfaces. Note that this relationship breaks down when the surface area gets too small, since then the coefficient of friction increases because the object may begin to dig into the surface.