The Magnus Effect

By Derek Teel
For Physics 211x Fall 2016
Instructor: David Newman



Introduction :

    Have you ever wondered why a ping pong ball behaves differently if you spin it before hitting it? Or maybe how a soccer ball curves when hit a certain way, or how an American football flies straight when a spin is added to it. I first noticed this effect when I was watching skilled table tennis players using their whole body to spin the ball. But why? Why do they use so much effort to change the spin? Well, in table tennis and a surprising amount of other sports spin is crucial in controlling the state of the game and making players behave how you want them to so you can have greater odds of victory.

    The effect behind this phenomena is the called  "The Magnus Effect."  I will provide various links     to help describe this effect contained in that tab. The               Magnus effect page will be describing the effect on various     sphereical objects and not entirely focusing on the effect it     has for ping pong.  Friction also plays a large part in the         trajectory of a ping pong ball upon impact. It can change         speed and even direction upon hitting the paddle or table.     For example top spin sends the ball down into the table and     upon hitting the table it speeds up much like how a car         accelerates forwards using friction and the rotation of the             Photo Credit:  http://fuckyeahphysica.tumblr.com/              tires.
   

    To the right is a picture describing the motion of the ping pong ball with the application of top spin. Notice how through the entirety of (1) the ball is basically carried by the force applied from the paddle. Then from (2)-(3) the spin of the ball starts to impact the direction of the ball. As the ball progresses further right the ball dives down into the table and upon hitting it (3) its spin takes a different effect. Instead of directing the ball downward in the air it                  Photo Credit: goes to https://en.wikipedia.org/wiki/Table_tennis produces friction with the table and propels the ball forward. Notice how at (4) the opponent angles their paddle down to counter the spin of the ball. Upon hitting the ball with the downward angle the ball changes direction and goes up. If you think about it the ball still has forward spin from the original hit, so when the ball hits the opponents paddle it wants to continue forwards, which would be upwards from the angle of the paddle.

Now that we have some background what the magnus effect looks like, lets see how it works.          

Magnus Effect