A mixing beater consists of three thin rods, each 10.6 cm long. The rods diverge from a central hub, separated from each other by 120, and all turn in the same plane. A ball is attached to the end of each rod. Each ball has cross-sectional area 3.80 cm2 and is so shaped that it has a drag coefficient of 0.580. The drag force on each ball is

R =

1

2

D A v2

where D is the drag coefficient,

the density of the fluid, A the cross-sectional area, and v the speed of the object moving through the fluid.