paragraph: Friction is a force that works against motion. It occurs between two surfaces that are touching. Friction can be good and bad. How can this be? Think about some common things we do. For example, we put rubber tires on our cars. The tires cause friction against the road. Without rubber tires, the car would slide around. Think about the bottom of your bathtub. Do you have tape that has a sandy texture? Maybe you use a rubber mat. Both materials prevent you from slipping. If you live in a really cold place, you have probably seen icy sidewalks. Perhaps you have put sand on the frozen surface. The sand increases friction. It helps to keep you from slipping and falling. Is friction always a good thing? Too much friction can also be harmful. 
question: What can be done to prevent falls on icy sidewalks?
answer: Put sand on the frozen surface