What is friction?

Friction: F = μ × N. Friction is the force that resists two surfaces sliding over each other. It grows with how hard they are pressed together (F = μ × N), hardly depends on how big the contact looks, and is what lets you walk, drive and grip anything at all.

Read how it works: What is friction? · The history of friction · More boxes on Glassbox

Chapters in this interactive model

1. The force that grips before it slips: Pull a block with a spring scale: friction matches you, up to a limit, then lets go.
2. Grip: how tyres drive, turn and stop: Every push that moves a car or a bike comes through a patch of rubber the size of your palm.
3. Friction we fight: wheels, bearings and oil: Rolling beats sliding, balls beat bushes, and a film of oil beats them all. What is left becomes heat.
4. Friction we need: walking, writing, knots and music: Take friction away and you couldn’t take a step, write a word, tie a knot or play a note.
5. Friction myths, and where the simple rule breaks: Area doesn’t matter, smoother isn’t always slipperier, and pressure doesn’t melt ice.