Bernoulli Air-Blower Ball

The hair-dryer trick: a light ball hangs in a jet of air and refuses to fall out, even when you tilt the stream sideways. Two things hold it. Vertically, the jet's drag pushes up; the jet slows with height, so there is exactly one height where drag equals the ball's weight, and it is stable, drift up and drag weakens so the ball sinks back. Sideways, the restoring force is the everyday Bernoulli effect: if the ball wanders toward the edge, the side facing the fast core meets faster air and lower pressure, and the pressure difference pushes it back to the middle. The scene shows the jet, colored by speed, cradling the ball; the diagnostic plots the upward drag against height and marks where it balances gravity.

Figure 1. A ball levitated in a turbulent air jet. Top: the jet, colored by speed, holds the ball; tilting the nozzle carries the ball with it. Bottom: the upward drag on a still ball versus height, crossing the weight line at the stable levitation height. Method: quadratic drag in a Gaussian free-jet, with a Bernoulli cross-jet restoring force.

blower18

tilt (deg)0

ball (g)2.7

WHAT TO TRY

Tilt the nozzle: the ball leans with the jet instead of falling out, the Bernoulli restoring force keeping it on the axis.
Lower the blower power: the drag curve drops, the balance height falls, and below a threshold the curve no longer reaches the weight line, so the ball drops.
Make the ball heavier: it needs more drag, so it sits lower in the faster part of the jet, until the jet cannot hold it at all.
Turn the blower off and watch it fall; turn it back on and the jet recaptures it.
Grab the ball and drop it off to one side: the jet tugs it back to the axis and settles it at the balance height.