Rolling and wheels in the natural world
Wheels can slip, meaning they fail to get a grip, on loose or slippery ground. Slipping wastes energy, and can lead to loss of control or becoming unable to move. This happens to cars on mud, ice, and snow. Where wheels have this problem, people sometimes use other mechanisms instead. In the logging industry, vehicles with legs are sometimes used to reach areas that are more difficult than what wheels can deal with. Vehicles with tracks, like tanks, don't slip as much as vehicles with wheels, because they have a larger area touching the surface. However, vehicles with tracks often have a larger turning radius than wheeled vehicles, meaning they take more space to turn. They are also less efficient, and more complex to build.