The Magnus Effect…

March 23, 2010 at 2:04 am Leave a comment

If you’re reading this I’m assuming you’re a fan of baseball.  If not, than I assume you searched “Magnus Effect” in Google and are now here.  Either way I will try to teach in an easy to understand way.

Ok first off I’m going to assume we’ve all seen a baseball game.  If not, go watch one.
Now having got that covered, did you notice how when the ball was pitched or hit, it’s destination was different than it’s initial trajectory?  That my friends is the result of the Magnus Effect.  It is the direct result of the force perpendicular to the forward motion on a spinning object moving through a fluid.  Basically, the spin of an object can effect how it moves through a liquid or a gas.
So now the question remains, how does it work exactly?
Lets use our imaginations for a second.
Imagine you have a baseball in your hand and you throw it forward with the only forces working on the ball are forward motion put by you on the ball, the resistance of the air you’re throwing it through, gravity, and the spin your fingers put on the ball.  Now it’s easy to imagine the ball moving forward, air resistance slowing it down, and gravity pulling the ball down, but think about the direction of the spin you put on the ball with your fingers.  If you’re picturing what’s in my head, there was no wrist movement on the pitch, so therefore the resulting spin on the ball is upward looking from the front face of the baseball.  The direction of the spin tells you how the Magnus Effect will effect the throw.
In technical terms the upward spin of the ball is creating a low pressure zone on top and a high pressure zone on the bottom of itself.  This pressure difference on either side of the baseball causes lift.  Because of that gravity thing, the ball doesn’t actually rise, but will remain in the air for a longer period of time than that of a of a ball thrown with no spin at all.
But really that isn’t a very visual throw.  Woo, the ball goes straight.  Lets talk about something interesting like, a curveball.
The above pitch we were talking about was essentially a fastball.  A straight, no frills, fastball.  Curveball’s are more fun because the spin put on the ball acts more parallel to the ground instead of perpendicular to it.  The resulting pressure zones cause horizontal movement instead of vertical making the pitch look a hell of alot cooler.
Just to kind of add some side info here, smooth objects tend experience less of this effect than rough objects.  With a baseball it’s the threads that help create this effect.
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Entry filed under: Terminology. Tags: , , , , .

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