You have been using an analogy between a row of sticky notes and the sandpaper surface to develop your ideas about how a frictional force is produced when a block slides across sandpaper. However, you have seen that even when the block slides across an apparently smooth tabletop, it still slows down. Consider how our analogy might be extended to explain how a frictional force is produced when the block slides across an apparently smooth surface. What do you think you would see if you looked at a smooth tabletop with a powerful magnifier? A A thin layer of moisture on the surface that makes it somewhat 'sticky' B. Very small bumps and grooves in the surface C. Nothing. It would still look perfectly smooth.