Question

Mark the correct statements about the friction between two bodies:
[a] Static friction is always greater than the kinetic friction.
[b] Coefficient of static friction is always greater than the coefficient of kinetic friction.
[c] Limiting friction is always greater than the kinetic friction.
[d] Limiting friction is never less than static friction.

• A. b, c, d
• B. a, b, c
• C. a, c, d
• D. a, b, d

Answer 1

The correct option is A b, c, d

Coefficient of static friction is always greater than the coefficient of kinetic friction because interaction between the surfaces is more established when the surfaces are at rest. But as normal forces can change, so same not hold in case of friction forces.
The maximum friction can be generated between two static surfaces in contact with each other. Once a force applied to the two surfaces exceeds the limiting friction, motion will occur. For two dry surfaces, the limiting friction is a product of the normal reaction force and the coefficient of limiting friction. So as coefficient of static friction is always greater than the coefficient of kinetic friction, therefore, limiting friction force is a product of the normal reaction force and the coefficient of static friction,Hence can never be less than static friction and always greater than kinetic friction.