Car manufacturers spend millions on streamlining cars for lower air resistence. But what is the most efficient shape for a car to be?
Look at water droplets travelling through air. As a liquid, surface tension keeps the molecules together as a drop. In a vacuum, water drops are spherical as surface tension forces minimise the surface area. Travelling through air, water takes on the characteristic tear-drop shape – air resistance flattens the front while forming a streamlined “tail” at the rear.
Liquids will take the shape created by the combination of the forces acting on it (eg. the edges and base of a glass combined with gravity). Thus a teardrop shape is probably the most efficient shape for an object to take while travelling through air. Similarly this should hold for submarines travelling through water.
Indeed dolphins and whales seem to be shaped a little like this as well – a large bulbous head tapering to a thinner tail.
Perhaps in the future, as fuel becomes more scarce and thus air resistance issues become more important for greater fuel efficiency, cars may look more like this as well.