Golf Ball Dimples

Podcast

Golf Ball Dimples

Transcript

Why golf balls have pockmarked complexions. I'm Bob Hirshon and this is Science Update.

Today's question comes from Timothy Nelson of Wasilla, Alaska.

Tim:
Why do golf balls have dimples on them?

We asked aerospace engineer Bob Thurman. He designs golf balls for Wilson Sporting Goods in Humboldt, Tennessee.

Thurman:
The dimples are there // to reduce the aerodynamic drag, that would be acting on the ball if it were entirely smooth.

He explains that when a smooth ball sails through the air, it leaves a big pocket of low-pressure air in its wake. That creates drag, which slows it down.

Thurman:
So if you can make that wake smaller, then the pressure differential goes down. So the drag force is actually reduced.

The dimples do this by creating turbulence in the air around the ball. That forces the air to hug the ball more closely. So instead of flowing past it, the air follows the curvature of the ball around to the back. The result is a smaller wake, and less drag.

Thurman:
A smooth ball when struck by a driver, would probably carry about 110 yards in the air and a well designed golf ball is going to carry 250 yards. So that's a huge difference.

Don't let your science questions drag you down. Call us at 1-800-WHY-ISIT. If we use it on the show you'll get a free Science Update mug. For the American Association For The Advancement Of Science,I'm Bob Hirshon.

Making Sense of the Research

A good walk ruined is how golf is often described. Yet, despite the frustrations involved in playing the game, golf has been around for a long time. Indeed, the game of golf seems to have existed since the 1400s. During that time, the make and shape of the golf ball has changed considerably. It started out as a wooden ball, then graduated to a ball with a leather case with feathery stuffing, then to a metal case with a rubber-like stuffing (called gutta percha), and then to the rubber core golf ball. The first balls were smooth. Golf balls with dimples started to be produced in the late 1800s. It was during the gutta percha phase that golfers noticed that their shots became more predictable as their balls roughened from play. The dimpled cover helped players to control ball trajectories with aerodynamic spin. It also helped players to put backspin on a shot, nearly stopping the ball dead on the putting green.

The story of the dimpled golf ball is a good way to illustrate some physics concepts concerning air pressure, turbulence, and aerodynamics. As in the Science Update on balloons, this story focuses on motion, particularly Newton's laws of motion.

As you read the transcript for this Science Update, keep in mind the following questions:

1. What is Bob Thurman's explanation for why golf balls have dimples on them?
2. What happens when a smooth ball sails through the air?
3. What do the dimples on a golf ball do to the air surrounding a golf ball?
4. How far can a smooth golf ball travel when hit by a driver?
5. How far can a dimpled golf ball travel when hit by a driver?

Going Further

For more explanation on golf ball dimples, you can visit How Stuff Works and read Why Do Golf Balls Have Dimples? You can find more information about the dimples on golf balls by going to Evolution of the Dimpled Golf Ball site.

For additional resources related to this topic, see Content Section: IV. The Physical Setting (Motion).