A. friction D. sliding friction B. lubricant E. fluid friction C. rolling friction F. static friction 1. It is a substance placed between two surface to reduce friction. 2. It is produced when you rub your hands together. 3. It is observed when two solid surfaces slide over each other. 4. It exists between the moving wheels of vehicles and the ground. 5. It occurs when the two objects in contact are not moving.
