Tuesday, December 23, 2014

Straw Spray Experiment

I credit students in my high school physics class for introducing me to this science experiment/demonstration.  They sent me a link to this YouTube video, provided below, and asked me if I could get it to work, because they were unable to reproduce the experiment.  The idea is to fill a glass full of food colored water and tape a straw vertically inside the glass.  Then take another straw and blow perpendicularly at the very top of the taped straw.  The physics says that blowing air across the top of the vertical straw reduces the air pressure at the top of the straw, causing liquid inside the straw to rise.  As the liquid rises to the top, the air blowing horizontally causes the liquid to spray outward onto the wall.

Being The Cool Science Dad that I am, I had my two daughters help me out with this task.  We set it up just as described in the video and I started to blow through the straw.  The result?  Nothing.  Hmmm....as any good scientist does, we started to investigate why it wasn't working.  We tried various things and eventually cut the straw inside the glass as short as possible.  This reduces the height the liquid in the glass as to rise.

The result?  It worked, although you have to blow very hard into the straw.  I was barely able to get it to work, and my daughters had no luck at all, but it worked!

Try it out yourself!  Just be sure to have towels ready because you'll be blowing liquid out of the glass onto the wall/floor.  It's a cool science experiment because you see water appear to magically rise up the straw and out of the glass.  I say 'appear' because it's not magic.  It's science!

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