You may have noticed that, in recent years, some competitive-level speed skaters wear body suits equipped with jagged ribbons on the forehead, such as the one indicated by an arrow in the figure. Similar ribbons are sometimes positioned on the calves and other parts of the body.
a) Explain the likely effect that such ribbons might have on the performance of the skater.
b) Approximating the skater’s head as a smooth sphere with a diameter of 0.25 m, estimate the range of speeds (in km/h) over which the ribbon would offer some advantage. Also estimate the range of speeds, if any, over which the ribbon may actually be of disadvantage.

Contributed by Stavros Tavoularis, Department of Mechanical Engineering, University of Ottawa, Ottawa, Canada.