Dimples and drag: Experimental demonstration of the aerodynamics of golf balls

While it is well known that the presence of dimples reduces the drag force exerted on a golf ball, demonstrations of this phenomenon are not common. A simple pendulum is designed and used in a wind tunnel to measure the drag force exerted by a moving stream of air on a spherical object. This pendulum is then used in experiments to measure drag forces exerted on smooth balls and on golf balls in order to compare the results. Data collected from 12 balls tested at speeds ranging from 54 to 180 km/h demonstrate that the presence of dimples on the surface of golf balls causes them to experience drag forces that are smaller than those on smooth balls of the same diameters and weights. (C) 2007 American Association of Physics Teachers.