Coefficient of Friction

What is Coefficient of Friction?

A dimensionless ratio relating the friction force between two surfaces to the normal force pressing them together. Static friction is always slightly higher than kinetic, which is why it takes more force to start an object sliding than to keep it sliding.

The five clues

Engineerdle #21 described Coefficient of Friction with five clues, revealed one at a time from hardest to most direct. Each clue points at a different property of the concept.

1. 01A dimensionless number with the symbol μ.
2. 02It comes in a static value and a slightly smaller kinetic one.
3. 03Multiply it by the normal force and you get the friction force.
4. 04Rubber on dry asphalt gives a much higher value than steel on ice.
5. 05F = μN.

More Dynamics concepts

• Center of MassPuzzle #16
• Newton's Third LawPuzzle #2