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Sliding Vs. Rolling
• Usually the force of sliding kinetic friction is greater than the force of rolling kinetic friction
When would sliding be easier?
Static friction – a force does not cause the object to move
• The force of static friction balances the force applied
• Turbulence factor• An interesting aspect of fluid friction is that setting up tiny areas of
turbulence on the surface will reduce the friction even more. A good example of that are the dimples on the surface of a golf ball. If an ball had a completely smooth surface, it would not fly as far as an identical ball with a dimpled surface. The reason is that each dimple creates a small area of turbulence on the surface. This means the air is then flowing over air in that area and not along the surface of the ball, thus reducing the resistive friction.
• Dimples on golf ball reduce surface friction• But note that if the dimples were too large or deep, then the
turbulence would cause the ball to slow down. Dimple dimensions and locations are very important in the design of golf balls.
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