Question

Intuition might tell us that rough surfaces on clothing would inhibit the speed of an Olympic athlete. Why is this line of thinking not true in some cases? How can controlled roughness actually promote speed?

Answer 1

The thinking that rough surfaces on clothing would inhibit the speed of an Olympic athlete may not be entirely be true in most cases because the drag that a person experiences is the effect of the air that he goes against and might not be affected by the clothing. 

The controlled roughness may promote speed as this would allow the person for the proper ventilation allowing his system to work well by allowing air to enter. 

Answer 2

Answer:

We associate roughness with a greater coefficient of friction, then we think that rough surfaces on clothing would inhibit the speed of an Olympic athlete.  This is not always true because the amount of roughness might improve the way air pass through the fabric.  

One example of controlled roughness that actually promote speed are the dimples on golf balls. Dimples create turbulence around the ball, which sucks air to the ball, making its displacement easier and promoting its speed.