Editing Sled (section)

==Operation==

Sleds are especially useful in winter but can also be drawn over wet fields, muddy roads, and even hard ground if one helps them along by greasing the blades ("grease the skids") with oil or alternatively wetting them with water. For an explanation of why sleds and other objects glide with various degrees of friction ranging from very little to fairly little friction on ice, icy snow, wet snow, and dry snow, see the relevant sections in the articles on [[Ice#Friction properties|ice]] and [[Ice skating#Physical mechanics of skating|ice skating]]. The traditional explanation of the pressure of sleds on the snow or ice producing a thin film of water and this enabling sleds to move on ice with little friction is insufficient. <ref>[https://www.vox.com/science-and-health/2018/2/13/16973886/why-is-ice-slippery "The surprising science of why ice is so slippery"]</ref>

Various types of sleds are pulled by animals such as [[reindeer]], horses, [[mule]]s, [[oxen]], or dogs.