Can a ball be shot around an object in an arc?

About ten years ago I asked a similar question, but with the question whether you can shoot a bullet around an object with a bow. The discussion arose again, but this time about a football player who, as it were, can shoot the ball around something in an arc. Is this possible?

Asker: Karen, 33 years old

Answer

Yes, you can because of the Magnus effect. In football it is usually used to deflect a ball to the left or right, for example to make the ball go around the luur on a penalty. In tennis or ping pong it manifests itself as topspin or backspin in which the ball deviates more or less downwards.

Let’s say you kick a ball away (roughly horizontal) and give it an extra spin around the vertical axis. Suppose, for example, that the right side moves in the direction of the ball’s movement, and the left side comes towards you. Facing the air through which the ball flies, the ball surface on the right side, the “fast side”, has a greater speed than on the left. The air on the fast side breaks away faster than the air on the slow side. The air on the slow side stays attached to the ball longer. The overall effect is that the air on the slow side is deflected more, and the law of action and reaction deflects the ball in the other direction. So from your point of view to the left.

A nice explanation with moving images and especially with a few clear and simple experiments can be found at (scroll down a bit until the video):

https://busy.org/@ttitto/the-magnus-effect

I would therefore like to refer to it.

You can test it yourself at home with a cardboard cylinder, for example from a roll of kitchen paper. Hold the roll in front of you and let it fall vertically while giving the roll a quick spin. If the roller at the top turns away from you, it will fall on your feet. If you spin the roller so that the top is facing you, it will fall further than right below the starting position. Some practice is required because you have to see that you don’t unintentionally give the role a push yourself when you let go, but if you do it a enough number of times, the difference will be clearly noticeable on average. Also spectacular is the experiment with a basketball that you can see at https://www.youtube.com/watch?v=QtP_bh2lMXc

Can a ball be shot around an object in an arc?

Answered by

prof.dr. Paul Hellings

Department of Mathematics, Fac. IIW, KU Leuven

Catholic University of Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/

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