I. the normal reaction between the surfaces
II. the area of surface in contact
III. the relative velocity between the surfaces
IV. the nature of the surfaces
A. I only
B. II only
C. III only
D. I & IV only
Correct Answer: Option D
D. I & IV only
Explanation
– Friction depends on the nature of the surfaces in contact
– Solid friction is independent of the area of the surfaces in contact and the relative velocity between the surfaces.