O_TEXTBLOCK_TEXT When glass rubs against glass, a very small amount of friction is produced, since their surfaces are smooth. Notice that when wood or rubber rubs against glass, wood, or rubber, more friction is produced. The bumps and holes of both surfaces catch on the bumps and holes of other surfaces, and there is <HL Topic=Resistance.tpc>RESISTANCE</HL> to <HL Topic=Motion.tpc>MOTION</HL>.
E_QUEST1 What would happen if there were no friction between a car's wheels and the road?
E_QUEST2 What happens to the soles of your shoes after you have worn the same pair for a long time? How is this related to friction?
E_QUEST3 Why is it easier to ride your bicycle after you have greased the chain? How is this related to friction?
D_TEXTBLOCK_TEXT Whenever the surfaces of two materials rub against one another, the <HL Topic=Resistance.tpc>RESISTANCE</HL> to movement is called friction. <HL Topic=Energy.tpc>ENERGY</HL> is released in the form <HL Topic=Heat.tpc>HEAT</HL>. Since the surface of every material contains bumps and holes, when two surfaces rub together, the bumps and holes catch and stick together, which makes it difficult to move one material over the other.
