Free
Have you ever watched someone raise a flag on a flagpole?
If so, you’ve seen a simple machine at work. That machine is the pulley. Pulleys, like wheels and axles, are circular levers. But the pulley wheel is a groove. The groove lets a rope or belt or chain turn freely. A pulley cuts out the friction that would result if the rope were pulled over a solid shape instead of a grooved wheel.
