RE: Golf ball dimples
<div style="margin: 0in 0in 0pt">Golf balls may be the only projectiles with dimples but they are not the only projectiles that benefits from having a rough surface. Any surface preparation that increases surface drag increases the Magnus effect such as dimples on a golf ball, fuzz on a tennis ball, threads on a baseball. Think of a spinning ball or cylinder as an air pump, the rougher the surface the more air the ball or cylinder can pump. A wing pushes (high pressure) and pulls (low pressure) air down to generate lift in the upward direction. A spinning ball or cylinder pumps air down by pulling on it to generate an upward force. This pulling is not characterized by low pressure it is more the result of the airs viscosity. So the wing and the spinning ball or cylinder can both do the same thing only one uses lift and the other uses viscous drag.A squirrel cage fan and a conventional house fan both do the same thing only one uses lift and the other uses drag. The paddle on a paddleboat and the propeller on a bass boat both generate thrust only one uses drag and the other uses lift. A round canopy and a square canopy parachute and a human body can all use still air to totally support their weight when dropped from height altitudes only two use drag and one uses lift and drag and one of em ain’t going to make it. </div>