Friction happens when two things touch or rub against each other.

What energy does friction often create (e.g. when we rub our hands together)?

Long ago, humans used friction to create fire.

Under magnification, even smooth surfaces appear rough.

What do football boots have to grip the surface well?

Rock climbers use chalk to increase their grip.

Friction on ice is high.

Skiers wax their skis to reduce friction.

What frictional force did the Egyptians use to build the pyramids?

Oil is used on machinery to increase friction.

Even air can create friction called air resistance.

What electricity is created because of the friction between socks and carpet?

Friction between clouds creates thunder and lightning.

Friction slows momentum but is also often essential for starting it.