Why ball turns when rotated after being kicked.

[exquisitenick]

Hello,
I have an unsolved question of an exam of my University.
The question is why a ball turns, when somebody kicks it by making it to rotate to itself.

[amppatel]

lol, doesnt really make sense. If you kick a ball head on ie perpendicular to the ball, then the ball will not spin. Unless there is unequal amounts of drag acting on either side, which is not really possible. The reason why a ball will spin is that the foot does not hit perpendicular to the surface and so give the ball some angular momentum.

[Cthugha]

lol, doesnt really make sense. If you kick a ball head on ie perpendicular to the ball, then the ball will not spin. Unless there is unequal amounts of drag acting on either side, which is not really possible. The reason why a ball will spin is that the foot does not hit perpendicular to the surface and so give the ball some angular momentum.

That does not even answer the question. The question was, why a spinning ball turns in flight like commonly seen in table tennis or banana kicks.

This is usually attributed to the Magnus effect, which is caused by the airflow, which has a different velocity compared to the center of the ball at both sides of the turning ball. However this also depends on some characteristics of the ball.

It is also described here: http://www.soccerballworld.com/Physics.htm

[rcgldr]

Magnus effect:

Wiki article, showing top spin in diagram, oversimplified Bernoulli based explanation.
http://en.wikipedia.org/wiki/Magnus_effect

Another article, showing back spin in diagram, and a more accurate explantion of Magnus effect:
http://www.geocities.com/k_achutarao/MAGNUS/magnus.html

[exquisitenick]

Thank you very much!

[LURCH]

Interesting side note (at least, I hope it's interesting):

On Mars, the ball would curve the opposite way (http://www.space.com/scienceastronomy/mars_curveballs_030221.html).