Free
Have you ever watched someone raise a flag on a flagpole?
If so, you’ve seen a simple machine at work—the pulley. Pulleys, like wheels and axles, are circular levers. But in this case, the pulley wheel is a groove in which a rope or belt or chain rotates freely. A pulley eliminates the friction that would occur if the rope were pulled over a solid shape instead of moving in a grooved wheel.
