Surfaces interact microscopically
Real surfaces have irregularities and molecular interactions that resist sliding.
Static and kinetic friction differ
The force needed to start sliding can differ from the force opposing an object already moving.
Friction converts energy
Mechanical energy often becomes thermal energy when surfaces rub.
Less friction is not always better
Bearings reduce unwanted friction, while shoes and tires need useful friction.
This page explains scientific concepts for general learning. It does not replace laboratory safety procedures, professional engineering guidance, or individualized medical advice.