id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
work_mkyhlq4vxjgl7oiv3etpc6js5q	John Eric Goff	Power and spin in the beautiful game	2010	2	.pdf	application/pdf	1883	129	77	As a soccer ball moves through air, it feels a force due to is the Reynolds number, Re = VD/ν, with V the ball's center-ofmass speed relative to the air and D the ball's diameter; the the diameter while doubling the speed maintains the same Re. The air's pressure and viscous interactions with the ball give rise to the drag force, which points opposite to the ball's After a ball leaves a soccer player's foot, surface roughness and boundary layer from a soccer ball moving ing soccer ball moving through the air. For soccer balls, the drag crisis sets in when the speed is major-league fastball, Re ≈ 2 × 105 and the drag force is comparable to the weight of the ball. Figure 2 shows a Gerrard-like free kick. time with Gerrard's spinning ball, whose banana-shaped trajectory not only curves as shown in the figure but actually	./cache/work_mkyhlq4vxjgl7oiv3etpc6js5q.pdf	./txt/work_mkyhlq4vxjgl7oiv3etpc6js5q.txt