Machines - how they work

A machine is any device used to change the magnitude or direction of an applied force. It is used to make tasks easier and less force-needing for humans, by transferring energy from one point to another. It’s main advantage is that it enables a person to exert a force greater than could be exerted by using muscles alone, or to apply a force more efficiently, as with the pulley. Machines don’t always have …

…exert five pounds of force to lift a one-pound can, but if the can is lifted one foot, the muscle only needs to contract one-fifth of a foot, a little over two inches. If the body were designed with a mechanical advantage of five, then the muscle would only have to pull with one-fifth of a pound of force, but it would have to contract five feet, and our elbows would drag across the ground.