Dynamics of Nature - Jack

This highly efficient rack and pinion device is the basis for the car jack in use today. It converts rotational motion into linear motion, and allows heavy objects to be lifted with a small amount of effort.
A crank is connected to a small gearwheel. When it is turned, the circular pinion engages the teeth on the rack, and moves it upwards. Any object on top of the rack is lifted in turn. The object can be lowered by reversing the direction that the crank handle is turned.