Why Does a Ball Spin When Thrown?

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SUMMARY

When a ball is thrown, it typically spins due to the mechanics of the throw, where the arm's motion imparts rotational force. This spin occurs even with minimal intention, as imperfections in grip and release can cause uneven contact with the fingers. The discussion also highlights that while a shotput may not spin significantly during flight due to its weight and throwing technique, most other balls, like baseballs and footballs, inherently acquire spin. The Magnus effect, while mentioned, is not the primary reason for the spin during the throw.

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  • Understanding of basic physics principles, particularly forces and motion.
  • Familiarity with the mechanics of throwing techniques.
  • Knowledge of the Magnus effect and its implications in sports.
  • Experience with friction and its role in ball movement.
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  • Research the physics of rotational motion in sports, focusing on ball dynamics.
  • Explore the Magnus effect in detail and its applications in various sports.
  • Study different throwing techniques and their impact on ball spin.
  • Investigate the role of friction in ball movement on different surfaces, such as pool tables.
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Sports scientists, physics educators, athletes, and coaches interested in understanding the mechanics of ball dynamics and improving throwing techniques.

nhmllr
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When you throw a ball, why does it spin?
Does it have to do with the air resistance?
Obviously, you can spin it when you throw it, but it seems to spin even if you just "push" it up.
Is it that I'm just not being precise here?
Is this related at all to why it's easier to balance on a bike when you're going faster?
 
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A ball doesn't have to spin when thrown. Look at a shotput. It doesn't spin much (if at all) while in flight. Usually a ball spins because when you throw it you put spin on it. Unless you shotput it then you are most likely throwing it similar to how you throw a baseball or football. Since your arm and hand are coming down or across, when you let go of the ball, you give it a final push to one direction as it is coming off of your hand/fingers which puts spin on it.

Take the game of Pool for example. If you hit the Q ball dead center, there is no spin that you introduce on the ball. The reason it rolls is because of friction on the table. But if you move your stick and hit it off center, then you can do all kinds of things due to putting spin on it. In general, you are putting spin on a ball when you throw it, even if it is just a little bit.
 
Usually when you throw a ball upwards without intending to spin it, it spins because of imperfection. You may have removed contact from one side of the ball while the other part just rolls on the fingers for a fraction of a second . Also you may have pressed the ball differently while holding.
 
Don't forget the http://en.wikipedia.org/wiki/Magnus_effect" .
 
Last edited by a moderator:
Magnus is the deviation of ball when spinning initially. It has nothing to do with this.
 
When you throw a ball, your arm is rotating so it is extremely difficult to throw it without spin. Shotputs are so heavy that you don't so much throw them as push them away from you.
 
Even if you could launch a ball with zero rotation, any nonuniformity of the air drag will start the ball spinning towards the side with the highest drag contact point...

well... assuming uniform airflow over the ball :P
 

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