|What is the "optimal" shape for a pinewood derby car — I'm guessing some sort of short, flat, thin rectangle. - BP
The car's biggest obstacle is air resistance, which in this case is a force known as "pressure drag." The pressure drag force is proportional to the size of the turbulent wake the car creates in the air as it passes through the air. Streamlining is important to minimizing this wake. The thinner and shorter you can make the car, the smaller its wake will be. The ideal shape would be an airfoil, like those used in airplane wings and bodies. These carefully tapered shapes barely disturb the air at all and experience very little pressure drag. If you design your car to resemble a wingless commercial jet airliner, you will be doing pretty well.