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Recently I have come across this interesting YouTube video regarding this phenomenon.

A huge ball is able to be levitated when a part of it is in contact with a water jet shooting upwards.

After some experimentation, I realised that hydrophobic(non water-absorbent) surfaces are able to exhibit this phenomenon, such as styrofoam and plastic, whereas cork did not work as well.

This has led me to believe that one of the forces responsible for keeping the ball in levitation is the adhesion between the water molecules and the surface. However, part of the puzzle still seems missing.

  1. Is the adhesive force solely responsible for keeping the ball/wheel up? Considering adhesive forces are relatively weaker than the weight of the ball, and that the ball’s COM is outside of the water jet, wouldn’t it fall?

  2. Upon external perturbations, such as pushing or pulling the ball out of its equilibrium, it is noticed that there’s is a restoring force. While the video cited above has mentioned that the water is responsible for pushing the ball back into its equilibrium position, it does not seem very convincing as the water droplets being thrown outwards are not exerting much of a force.

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