How does the limiting value of static friction depend on the area of contact?
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A.
Independent of area
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B.
Directly proportional to (area)2
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C.
Inversely proportional to area
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D.
Directly proportional to area
Correct Answer:
A. Independent of area
Explanation:
The limiting value of static friction is independent of the apparent area of contact between two surfaces. This occurs because, for a given object, increasing the surface area simultaneously decreases the pressure exerted on that surface. Since pressure is defined as force divided by area, the larger contact area is exactly offset by the lower pressure at each point of contact. On a microscopic level, friction is determined by the real area of contact (the interaction of microscopic peaks and valleys), which depends on the normal force rather than the total geometric surface area. Therefore, as long as the normal force and the materials remain constant, the total frictional resistance does not change with the size of the contact area.
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