The optical illusion of a curveball

novelist_wannabe · May 17, 2009

three_bags_full said:

novelist_wannabe said:

three_bags_full said:

The ball curves because the spinning motion creates lower pressure beneath the ball, and it moves toward the lower pressure. Just like a helicopter flies.
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This could get almost existentially deep, but I'm not sure the same thing is happening. What happens with aircraft wings and helicopter blades is explained under Bernoulli's Principle, which is along these lines: The top of the wing, because of the way it is shaped, is longer from front to back than the bottom. But the top and the bottom are traveling through air molecules at the same speed, and the air molecules, in simple terms, spread out; the top molecules move faster than the bottom ones. The result is lower air density above the wing, and the higher air pressure below the wing creates lift.

I don't think the same thing is happening in a spinning baseball; the top half of the ball has the same dimensions as the bottom half. I think the curvature of a thrown baseball has more to do with internal rotational momentum than it does with external air density. This article attempts to explain it using something called Magnus Force: http://webusers.npl.illinois.edu/~a-nathan/pob/AJPFeb08.pdf. It may require advance medication with ibuprofen though.
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The top and bottom half of airfoils aren't necessarily differently shaped. Only asymmetrical airfoils have different shapes. Many aircraft still use symmetrical wings/rotors/props.

When the seams on a baseball rotate to the top, a difference of pressure HAS to be created because a new shape, or air foil, is presented for the air molecules to act upon.

Maybe not. That's just the way I look at it.
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We're interrupting a quality Major League threadjack here, but I would argue the seams have little to do with it. The travel arc of other spheres without seams (billiard balls, bowling balls) is also altered by spin. Of course, they are also altered by their contact with the floor or table. To me the bigger myth is the "straight" fastball. All projectiles, if I'm remembering physics 101 correctly, travel in a parabolic path.

Baron Scicluna · May 17, 2009

And to think, it was all started by a guy named Candy throwing seashells on the beach.

Starman · May 17, 2009

three_bags_full said:

novelist_wannabe said:

three_bags_full said:

The ball curves because the spinning motion creates lower pressure beneath the ball, and it moves toward the lower pressure. Just like a helicopter flies.
Click to expand...

This could get almost existentially deep, but I'm not sure the same thing is happening. What happens with aircraft wings and helicopter blades is explained under Bernoulli's Principle, which is along these lines: The top of the wing, because of the way it is shaped, is longer from front to back than the bottom. But the top and the bottom are traveling through air molecules at the same speed, and the air molecules, in simple terms, spread out; the top molecules move faster than the bottom ones. The result is lower air density above the wing, and the higher air pressure below the wing creates lift.

I don't think the same thing is happening in a spinning baseball; the top half of the ball has the same dimensions as the bottom half. I think the curvature of a thrown baseball has more to do with internal rotational momentum than it does with external air density. This article attempts to explain it using something called Magnus Force: http://webusers.npl.illinois.edu/~a-nathan/pob/AJPFeb08.pdf. It may require advance medication with ibuprofen though.
Click to expand...

The top and bottom half of airfoils aren't necessarily differently shaped. Only asymmetrical airfoils have different shapes. Many aircraft still use symmetrical wings/rotors/props.

When the seams on a baseball rotate to the top, a difference of pressure HAS to be created because a new shape, or air foil, is presented for the air molecules to act upon.

Maybe not. That's just the way I look at it.
Click to expand...

Laminar surface drag creates pressure differential.

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The optical illusion of a curveball

novelist_wannabe Well-Known Member

Baron Scicluna Well-Known Member

Starman Well-Known Member

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The optical illusion of a curveball

novelist_wannabe Well-Known Member

Baron Scicluna Well-Known Member

Starman Well-Known Member

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