Last semester, I learned that the dimples on golf balls and the fuzz on tennis balls make the balls go faster by inducing turbulent flow at a lower speed than it otherwise would. Turbulent flow reduces the drag on the object. When automobile engineers design cars, they seem to make them as smooth as possible. In many car commercials, they show the car in a wind tunnel with perfectly laminar flow passing by. If turbulent flow decreases drag, why don't car manufacturers design their cars to promote turbulent flow at lower speeds? Maybe a rough patch at the front. I'm sure my sophomore level of understanding is the problem, not the engineers who do this for a living. I assume a more laminar flow is better for cars, since that is what the engineers seem to strive for. But what makes a car different from a tennis ball aerodynamically? Why is a turbulent flow better for a ball and a laminar flow better for a car?