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[Physics] Make my balls wobble
Improvolone
Registered User regular
Registered User regular
I'm trying to make a racquetball that will wobble signifigantly (erratic flight pattern) when thrown. Unlike a soccer ball, ping pong ball, or baseball, the ball won't be moving at very high speeds (won't be used in a game).
I already tried cutting out a section of the ball and placing a C battery in there and taping it shut, thus putting a whole lot of weight on one side. Even if I try to give the ball alot of spin when it leaves my hand, it's flight pattern stays fairly true.
I know I know, gravity is constant and all that, but my memory of childhood toys reminds me of balloons that wobble. Maybe the weight inside needs to shift?
Hmm, a ball is going to rotate around it's center of balance given limited air resistance (which is the case at low speeds), so I need a way to make a shifting center of balance?
Edit: A friend is suggesting cutting open the ball and putting in it a motor which turns a wheel with a weight on one side. This is starting to get awesomely complicated. I might need a bigger ball.
I already tried cutting out a section of the ball and placing a C battery in there and taping it shut, thus putting a whole lot of weight on one side. Even if I try to give the ball alot of spin when it leaves my hand, it's flight pattern stays fairly true.
I know I know, gravity is constant and all that, but my memory of childhood toys reminds me of balloons that wobble. Maybe the weight inside needs to shift?
Hmm, a ball is going to rotate around it's center of balance given limited air resistance (which is the case at low speeds), so I need a way to make a shifting center of balance?
Edit: A friend is suggesting cutting open the ball and putting in it a motor which turns a wheel with a weight on one side. This is starting to get awesomely complicated. I might need a bigger ball.
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Your best bet is alter the surface of the ball. That affects how the air behaves when passing over it. The seams in a baseball allow for different pitches depending on how you throw the ball, for example. Altering the moment of inertia (adding a weight inside) shouldn't do too much aside from having it drop more quickly.
One of us had a profound misunderstanding of 7th grade science class
One of us has a profound misunderstanding of rotational inertia.
If he adds a lot of weight to one side, it'll affect its air time (moment of inertia affects rotational speed affects pressure differential/Bernoulli Effect affects lift affects air time). In either case, though, it's effect on wobbling is probably minimized depending on how hard the ball's being thrown.
Drop a feather.
Drop a feather with a rock taped to it.
Don't do it inside a vacuum.
Think about it :P
As for the OP. I think your buddy is right in that you need a device within the ball that will move on it's own. If you simply put stuff inside the ball and throw it, both objects will be accelerated the same and fly together. You need something that will bang around the inside on its own. Maybe a motorized weight will do it? I have no idea.
At slower speeds... is it ok to roll the ball on a surface? If so, you could just fill it partially with water. Rolling something slowly with water in it makes it wobble fairly erratically.
But i'm crap at physics, so i've no idea if this is what you're after or anything
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A spinning object will rotate around its center of mass. If you can move the center of mass significantly, it will have a noticeable wobble if thrown correctly. However, with something as small as a racquetball, you'd need a pretty dense weight to move the center a significant amount. Best thing I can think of offhand would be a lead fishing weight. Maybe also thin out the ball on the opposite side (shaving from the inside if you can manage it).
Also possible would be to put a ball bearing inside without securing it. Then get it spinning around inside the racquetball before you throw it. If the ball bearing is massive enough compared to the racquetball, then once it's out of your hand, the racquetball will noticeably begin rotating around the ball bearing.
Another thing that might be neat to try would be to stick a toy gyro inside a ball in such a way that you can pull the cord once it's inside the ball. It won't wobble, but it will have a curving flight path.
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