Forces in Moving Fluids Concept

Demonstrations in Forces in Moving Fluids

Purple beach ball suspended in a tilted airstream from a handheld Ryobi leaf blower, with a chalkboard in the background
Safety

Leaf Blower and Beach Ball

Bernoulli's principle and the Coanda effect stabilize a beach ball in a leaf blower's airstream. Students predict which ball — light or weighted — remains stable at larger tilt angles, …
Sheet of white paper taped to a green lecture bench, drooping over the front edge, with a person holding a rubber hose at the far end of the bench
Safety

Paper Lift

A jet of compressed air blown across a bench lifts a drooping sheet of paper, demonstrating Bernoulli's principle. Students observe the counterintuitive result that fast-moving air above the paper creates …
Wooden thread spool with central bore next to a white card with a thumbtack hole in the center

Spool and Card

Blowing air through a spool holds a card against it rather than blowing it away, demonstrating that high-velocity flow creates low-pressure regions (Bernoulli's principle). Works even with the spool inverted.
Two-panel photo: Left — two ping-pong balls hanging from strings on a rod stand at rest. Right — a hand holds a hose with barb nozzle positioned between the balls.

Attracted Ping Pong Balls

Demonstrates Bernoulli's principle: blowing air between two suspended ping-pong balls creates a low-pressure region that draws the balls together. The counterintuitive result challenges students' expectations that the airstream should push …
Cardboard tube with sandpaper lining lying horizontally next to a pink ping pong ball on a gray surface

Curve Ball

Demonstrates the Magnus effect: a spinning ping pong ball curves through the air due to the pressure differential created by its rotation. Students observe how spin direction determines curve direction, …
Four white foam cups glued base-to-base and rim-to-rim, forming a column with two bulges at the rims and narrow waists at the bases, standing vertically on a green surface

Foam Cup Curveball

Demonstrates the Magnus effect: a spinning object falling through air experiences a lateral force due to asymmetric pressure from the interaction of rotational and translational flow. Connects directly to curveballs, …
Three dark red plastic coffee can lids on a white surface: left has intact rim, center has partial rim with tab cutouts, right has rim fully removed

Flying Disk Stability

Demonstrates how the rim of a flying disk provides aerodynamic lift that stabilizes flight. Three coffee can lids with different rim configurations are thrown like frisbees; the intact lid flies …