Understanding Friction

What Are Contact Forces?

When something moves, like a sled sliding down a hill, it slows down and stops at the bottom. This happens because of friction.

Friction is a type of contact force. A contact force happens when two things touch or rub against each other. In the case of the sled, the ground rubs against it, causing it to slow down. Friction works in many ways to stop or slow things, like brakes on a bike or the rubber soles on your shoes when you stop running.

Friction is important because it keeps things safe by helping them stop instead of sliding forever.

Are you ready to answer questions?

What is friction?

• A force that pushes objects into the air

• A force that happens when two things rub together

• A force that pulls objects toward the ground

Why does a sled stop at the bottom of a hill?

• Because of gravity

• Because of friction

• Because of the wind

What kind of force is friction?

• A contact force

• A pulling force

• A force that makes things float

How does friction help us?

• It makes things go faster

• It keeps objects moving forever

• It helps slow down or stop things

Which of these examples shows friction at work?

• A sled slowing down on the snow

• A kite flying in the air

• A ball floating in water

Low friction happens when two surfaces slide or roll past each other easily, with little resistance.

Choose two surfaces where friction is low.

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High friction occurs when two surfaces resist motion because they are rough or have a large contact area. It makes objects harder to move.L

Choose two surfaces where friction is high.

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