Which type of friction describes resistance to motion when there is no relative motion between surfaces?

Which type of friction describes resistance to motion when there is no relative motion between surfaces?

• A. Static
• B. Rolling
• C. Kinetic
• D. Viscous

Answer: (A)

Static friction is the force that resists the initiation of motion between two surfaces in contact when there is no relative motion. It can adjust up to a maximum value, μ_s times the normal force, to match the applied push. If you push harder than that maximum, motion starts and kinetic friction takes over. This is why it specifically describes resistance when there is no slipping between the surfaces. Rolling friction is the resistance you feel when an object rolls, due to deformation and other losses at the contact, not from preventing initial motion. Kinetic friction is the friction seen when surfaces actually slide past one another. Viscous friction occurs in fluids and depends on velocity rather than the onset of motion.

Static friction is the force that resists the initiation of motion between two surfaces in contact when there is no relative motion. It can adjust up to a maximum value, μ_s times the normal force, to match the applied push. If you push harder than that maximum, motion starts and kinetic friction takes over. This is why it specifically describes resistance when there is no slipping between the surfaces.

Rolling friction is the resistance you feel when an object rolls, due to deformation and other losses at the contact, not from preventing initial motion. Kinetic friction is the friction seen when surfaces actually slide past one another. Viscous friction occurs in fluids and depends on velocity rather than the onset of motion.