TBR: Golf Ball Dimples

[justadream]

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TBR Physics Book I page 53

"The golf balls used in the test have dimples distributed across their surface in a distinctive aerodynamic pattern to increase flight time. These dimples creates additional collisions with air if the ball is spinning"

My question: Do the dimples increase flight time if the ball is NOT spinning with backspin?

 

[Cawolf]

No - the dimples will not increase lift without backspin on the ball. The spin is required for the dimples to cause a pressure differential.

 

[justadream]

@Cawolf

So if I hit a ball with dimples vs. a ball with no dimples, they have identical flight? (assuming mass differences are negligible)?

 

[Cawolf]

Not quite. If you were to strike a ball so it had no spin, the dimpled ball would still travel farther.

This is because the dimples decrease the drag force on the ball. It is better to just look up a diagram (I am sure one can be found), but what I learned was that the dimples change the wake pattern - so the drag force is reduced.

Edit: This picture shows how a boundary layer of turbulence effects the wake, and therefore the drag force.