Friction

Friction is a force that happens when two things rub against each other. It slows moving things down or stops them. Rough surfaces have more friction than smooth ones. Friction can also make things warm. When you rub your hands together fast, they feel hot.

Why Friction Matters

Friction helps us walk without slipping. The soles of your shoes grip the ground. Without friction, everything would slide around. Brakes on a bike or car use friction to stop the wheels. Even writing with a pencil works because of friction between the lead and paper.

Less Friction

Sometimes we want less friction so things can move easily. Ice has very little friction, which is why we can skate on it. Oil and grease are slippery and lower friction in machines. Smooth, round wheels also help reduce friction. That is why cars roll so easily on roads.

Fun Facts

• Rubbing two sticks together can make enough friction to start a fire.
• Friction is what wears down the bottoms of your shoes over time.
• Space rockets get very hot from friction with the air when they return to Earth.

Did You Know?

Without friction, you would not be able to pick up a cup because your fingers would slip right off it.