Static friction is defined as the force exerted between two surfaces by weight alone, standing still (most difficult).

• A. Force that resists motion when the surfaces slide past each other
• B. Force that resists motion when objects are in contact at rest
• C. Force exerted between two surfaces by weight alone, standing still (most difficult)
• D. Force due to surface lubrication

Answer: (C)

Static friction is the force that resists the start of relative motion between two surfaces that are in contact and at rest. It can adjust its magnitude from zero up to a maximum value (μsN) as you push, preventing slipping until the applied parallel force exceeds that maximum. The key idea is that this friction exists while the surfaces are not sliding, not during sliding. On a horizontal surface, the normal force N is simply the weight, which is why weight is often tied to static friction, but the essential point is the resistance to motion at rest, with magnitude limited by μsN. The other descriptions mix in motion after contact (kinetic friction) or refer to lubrication, which changes friction but doesn’t define static friction itself.