Why does a spinning egg stand up?

If a hard-boiled egg is spun fast enough on a table, it will slowly stand upright as it continues to spin. Although the spinning egg rises due to the force of friction between the egg and the table, the full explanation involves ...

Solving the pancake problem

If you swirl a glass of wine clockwise, the wine inside will also rotate clockwise. But, if you're making a blueberry pancake and you swirl the pan clockwise, the pancake will rotate counterclockwise. Don't believe us? Go ...

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Friction is the force resisting the relative lateral (tangential) motion of solid surfaces, fluid layers, or material elements in contact. It is usually subdivided into several varieties:

Friction is not a fundamental force, as it is derived from electromagnetic force between charged particles, including electrons, protons, atoms, and molecules, and so cannot be calculated from first principles, but instead must be found empirically. When contacting surfaces move relative to each other, the friction between the two surfaces converts kinetic energy into thermal energy, or heat. Contrary to earlier explanations, kinetic friction is now understood not to be caused by surface roughness but by chemical bonding between the surfaces. Surface roughness and contact area, however, do affect kinetic friction for micro- and nano-scale objects where surface area forces dominate inertial forces.

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