what form of energy does friction always produce ?
Friction converts useful kinetic energy (also called ordered energy) into thermal energy (disordered energy), or heat. Friction gets a bad rap for turning useful energy into useless energy. It's true that a lot of kinetic energy in the world is lost into the atmosphere as heat. But heat isn't always useless. For instance, whenever our hands get cold, we can rub them together and feel the heat from the friction almost immediately.