Which of the following statements about friction is correct?

Explanation:

Friction is independent of the surface area in contact.

• Friction depends primarily on the normal force (the weight or force pressing the two surfaces together) and the nature of the materials in contact, but not on the surface area in contact.
• Increasing the surface area does not directly affect the frictional force.

 Additional Information

• Static friction is usually greater than kinetic friction.
• Static friction resists the initial motion of an object, while kinetic friction acts once the object is in motion, and is generally lower than static friction. 
• Friction depends on the nature of the surfaces in contact (roughness, material type, etc.). The coefficient of friction varies with the materials involved.
• Friction is directly proportional to the normal reaction force (the force pressing the surfaces together). The greater the normal force, the greater the friction.