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Dimpled Cars

December 12, 2006

A listener asks: Would the dimples on a golf ball also speed up a car or an airplane?


Should NASCAR imitate golf? I’m Bob Hirshon and this is Science Update.

If dimples make a golf ball fly farther, shouldn’t racecars and airplanes have dimples too? That’s a question submitted by listener Rich Jensen, and we posed it to Boeing aeronautics engineer Scott Eberhardt. He explains that dimples jostle the air as it rushes over the ball’s surface. That air turbulence disrupts and shrinks the ball’s wake, which reduces drag, but it also creates more surface friction, which adds drag.

But on a golf ball, it’s the wake that dominates, so you want to decrease the wake. So it’s okay to make it turbulent.

Conversely, on a larger object like a racecar or an airplane, surface friction matters a lot more than the wake. So covering it with dimples wouldn’t really help, and might even slow it down. If you’ve got a science question, call us at 1-800-WHY-ISIT. If we use it on the air, you’ll win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.