Dancing Balls Lead to a Physics Discovery

Have you ever seen how droplets of water react in a hot pan? The droplets appear to “bounce” on the pan. They move around quickly and energetically.

This experiment working with balls of hydrogen appear to produce the same “bouncy” effect, as well as an ear-piercing, shrieking noise. Hydrogen balls are basically water with a bit of polymer holding them together. This experiment is interesting in the sense that the hydrogen balls fully bounce up to heights several times their diameter. The bouncing and ear-piercing shriek noise produced by the hydrogen balls last until the hydrogel eventually ruptures, which could occur after more than 1,000 bounces. It is expected for the hydrogels to lose energy, however, they gain energy from the hot pan and eventually bounce higher.

This experiment is due to the Leidenfrost effect, which is a term used to describe the instant vaporization that occurs when water touches a hot surface. When a hydrogel initially hits the hot pan, a burst of vapor is created and deforms the ball. The ball’s elastic nature is able to store this energy by bending the ball inwards, and quickly springing it back, to ultimately provide a sudden kick which propels the ball back into the air. The screaming noise is caused by trapped vapor under the ball that is being released.

The results from this experiment could be a breakthrough in transforming heat into motion from heating coils or hydrogels. Researchers say that this could help power robots of the future, providing motion through the transfer of heat, without using bulky motors. The possibilities are endless, and the breakthrough from this “simple” experiment tell us just that.

http://blogs.discovermagazine.com/d-brief/2017/07/26/physics-dancing-balls/#.We1TY4ZrxbU

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