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Magnus Effect (Read 7190 times)
Matthias
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Re: Magnus Effect
Reply #15 - Jun 14th, 2006 at 1:57am
 
Disks, cards, and frisbees are working under a completely different set of conditions than a spinning ball. We spent weeks on this stuff at school, and I've unsuccesfully spent hours trying to explain the concepts that are used to describe/calculate lift. We covered the basic ideas here before though, and Dale's explanation can help with Tint's question.

The lift created is caused by the spinning, not the surface speed. If you throw a CD, or a right hand frisbee backhand, the tiny amount of lift due to the Magnus effect would pull the disk to the right. The surface that matter here is the thin edge of the CD, not the flat sides.

A thrown frisbee or playing card curves due to a completely different set of tricks. If you can throw it perfectly flat, a backhand will tilt to the right for the first part of the throw, causing it to veer that direction, then as it slows down it will flip back over to the left. A well thrown frisbee will fly in an 'S' shaped path. The changes in attitude are due to a combination of the angle of attack changes and gyroscopic precession.

On top of that, any angle you start the throw with adds its effect as well, just like banking an airplane.

In other words - it's magic.  Undecided

Matthias
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Tint
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Re: Magnus Effect
Reply #16 - Jun 14th, 2006 at 2:26am
 
magic!!! Shocked

oh! Roll Eyes

I thought I was just stupid, now I feel better. Grin
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Yahweh Bless you in Yeshua
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Re: Magnus Effect
Reply #17 - Jun 14th, 2006 at 3:11am
 

I agree with Matthias.....it is magic!  And David Copperfield don't hold a candle to it's Magician!


Wink


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Gard
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Re: Magnus Effect
Reply #18 - Jun 14th, 2006 at 1:44pm
 
What is meant by back spin and under spin and all those? How does the projectile really spin?

Throwing a card so that it spins clockwise will make the shape of the card not matter that much, and will make it more stable in the air. If you put a small weight at one side of a frisbee: Try throwing it without adding spin to it, it'll turn around and fall down. If you throw it so that you do add spin to it, it will be pretty stable in the air.

Gard
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Dale
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Re: Magnus Effect
Reply #19 - Jun 14th, 2006 at 5:36pm
 
A picture is worth a thousand words...
...
From left to right: back spin, top spin, football spin.

The ball with a backspin is lifted up.

The ball with a topspin is pushed down to the ground.

The ball with a football spin is pushed off to the side, but not very much (because its SIDEWAYS speed through the air is practically zero).

WRONG!  The ball with a football spin is not pushed any direction at all, because the forces are balanced.

But a ball with a sidespin would be pushed to one side or the other.
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« Last Edit: Oct 27th, 2006 at 2:53pm by Dale »  

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Gard
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Re: Magnus Effect
Reply #20 - Jun 14th, 2006 at 5:49pm
 
Ok, that cleared up a lot. Smiley

The clockwise spin is pretty powerful I've noticed. Once I was aiming for a tree 20 meters from me, and when the stone was in the air I could see that I was going to miss with more than a meter to the left. Well, halfways it screwed back and hit the tree just at the middle.

The football spin just makes the projectile more stable, doesn't it?

Gard
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Dale
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Re: Magnus Effect
Reply #21 - Jun 15th, 2006 at 1:00pm
 
Gard,
You are right.  If the axis of spin is at right angles to the line of flight, the ball will curve.  As any baseball pitcher knows, if you spin the ball to the right or to the left, you get a curveball.  And if the axis of spin is in line with the line of flight, it stabilizes the ball, as any football quarterback or rifleman knows.
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Re: Magnus Effect
Reply #22 - Nov 5th, 2006 at 1:31am
 
Just an idea.  I was wondering why the some of the old middle eastern/ Mediterranean  cultures changed from pouch and cord slings to strap slings.  Zwiebeltuete has made a beauty and in the "strip sling" thread on this forum gives this link slingshttp://www.mbsks.franken.de/slinging/slinging.html#LaterRomanSling ;  to pictures and more details.   Logically the less air resistance on the cords the better for speed of cast.  Presumably it was considered an upgrade.  Maybe it was the Magus effect that they were after, with an overhead cast, which many of the old Egyptian reliefs seem to depict, the release cord may drag on the top of the projectile thus imparting backspin.  I can do a bit of backspin with my standard slings but not much, however, a few dozen times I've flucked really strong backspin and the trajectory is wonderfully flat for a long way, I love to be able to do it to order.
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