Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/383

Rh effective value = .0125 (see § 182); it is also supposed that the tangential velocity of the air is proportional to $$\cos \beta$$—that is, equal to $$V \cos \beta .$$ The two curves thus plotted are given in Fig. 150.

Now, it is evident that the curve (b) (dotted line) corresponds more closely to the actual observed values than the curve (a), and we have certainly here primâ facie evidence of a tangential force about equal to that which we have assumed, and which is deduced from the author's own experiments.