This is an astonishing demonstration of the <a href="https://en.wikipedia.org/wiki/Coand%C4%83_effect" class="extiw" title="w:Coandă effect">Coandă effect</a>. The pingpong ball “sticks“ to the lower side of an airstream: The Coandă-Effect (in combination with the Robins-Magnus-effect) deters the ball from falling down, the jet as whole keeps the ball in some distance from the jet exhaust and gravity lets the ball not be blown away. So the ball may stay in a stable position.
<a href="https://de.wikipedia.org/wiki/Benutzer:Helmut_Stettmaier" class="extiw" title="de:Benutzer:Helmut Stettmaier">Helmut Stettmaier</a>
<span class="int-own-work" lang="en">Own work</span>