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Types of Friction

Introduction to static, sliding, rolling, and fluid friction.

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Benefits of Dimples

Credit: Goele
Source: http://commons.wikimedia.org/wiki/File:Red_Golfball.jpg
License: CC BY-NC 3.0

Most golf balls are white, but this red ball is clearly a golf ball. You can tell from the familiar dimples on its surface. Why do golf balls have dimples?

Why It Matters

  • If you play golf, then you know that being able to hit the ball farther may help you win a game. But no matter how hard you hit a golf ball, it will be slowed down by fluid friction with the air. This is also called air drag or air resistance. It is caused by friction between the ball and molecules of air. It slows down the ball and reduces the distance it travels.
  • Credit: Fevi in Pictures
    Source: http://www.flickr.com/photos/fevisyu/2335224771/
    License: CC BY-NC 3.0

    Inverted dimple golf balls were invented in the early 1900s and has been in use since then[Figure2]

  • Dimples on the surface of a golf ball reduce air drag. In fact, they reduce it by about half. In other words, a dimpled golf ball is almost twice as slippery as it moves through the air as a golf ball without dimples.
  • Watch this video to see how dimples affect the flow of air over the surface of a moving golf ball: https://www.youtube.com/watch?v=LvVuuaqCC7A

Can You Apply It?

Learn about another way dimples might be used at the link below. Then answer the questions that follow.

  1. Teen engineer Daniela Jiminez came up with the idea to use dimples to reduce air drag in another application. What was it?
  2. What is the key to reducing air drag on a moving object?
  3. What hypothesis did Daniela test with her experiments?
  4. How did Daniela test her hypothesis?
  5. What were the results of Daniela’s experiments?
  6. What did Daniela conclude about dimples in trucks and fuel efficiency? How would dimples help conserve energy?

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Image Attributions

  1. [1]^ Credit: Goele; Source: http://commons.wikimedia.org/wiki/File:Red_Golfball.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Fevi in Pictures; Source: http://www.flickr.com/photos/fevisyu/2335224771/; License: CC BY-NC 3.0

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