Question

If \(f_{s}\) and \(f_{k}\) represent the coefficients of static friction and kinetic friction of the relative motion between two surfaces in contact with area A, then

• A. \(f_{s}\) depends on A
• B. \(f_{k}\) depends on A
• C. \(f_{s}\) and \(f_{k}\) are independent of A
• D. \(f_{k}\) is greater than the maximum value of \(f_{s}\)
• E. \(f_{k}\) opposes impending motion

Hint:

Friction depends on normal force and surface roughness, not on contact area.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Coefficients of friction depend only on the nature of the surfaces, not on the area of contact.

Step 2: Detailed Explanation:
\(f_s\) and \(f_k\) are dimensionless constants. They do not depend on the area of contact.
Friction force = coefficient \(\times\) normal force, independent of area.

Step 3: Final Answer:
\(f_s\) and \(f_k\) are independent of A.