The Laws of Physics

tamiby: Tami O’Connor

My husband and I just returned from his reunion at Cornell University.  He attended the law school, so, while he reminisced with his friends about this loophole and that exception, I became curious about other events being held at the university.  I scanned the various offerings, and though he was interested in the course entitled “Effective Strategies for Conducting Online Legal Research”, the class entitled “Favorite Physics Demonstrations” at 2:00 PM jumped off the page at me.  The immutable laws of physics were just the diversion I needed! I made my way to the Physics building, arriving early.  I found plenty of hands-on materials placed all around the lecture hall for the spectators to “play” with.  To my delight, I had a “reunion” of my own with many products from Educational InnovationsSinging Rod! Air ZookaTornado TubesSound Tubes!  A Hand-Cranked generator!  And more…  All my old friends were here! The presenter’s table was covered with classic physics demonstration items: a Van de Graaff generator, bicycle wheels, magnets, and a host of other items. He had sound devices, and a table covered with glasses filled to varying levels with water.  From the 30’ ceiling hung a cable with a ball weighing about 10 pounds.  Fog leaked from a container of liquid nitrogen, and a large wooden box stood nearby.  I just knew it would be a fun afternoon!

Laws of Physics

What do paint and perfume have in common?  Using Bernoulli’s principle, the presenter, Dr. Philip Krasicky demonstrated how, when air flows faster, its pressure decreases.  Using two wide-diameter McDonalds’ straws, he stuck one in a glass of water.  With the other, he blew across the open end of the first straw.  With the resulting low air pressure, water rose in the straw and sprayed, via the stream of air, onto the front row spectators.  He explained that devices like paint sprayers and perfume atomizers employ this principle to spray their products.  Clearly, these were some laws we could rely on!

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Science Never Sucks | Milk Bottle and Egg

Tami O'Connorby: Tami O’Connor

One of my all time favorite air pressure activities is an oldie and a goodie!  It involves getting an egg into a classic, hard-to-find milk bottle, like the ones Milk Bottle and Egg Demodelivered to grandma’s door.  Unfortunately, some students (and some teachers) still think an egg can actually be sucked into a bottle.  As you probably know because the air pressure is greater outside of the bottle than inside, the better explanation is that the egg is literally pushed into the milk bottle.

Here is the explanation… The milk bottle and egg demo begins by placing two or three burning matches or a burning strip of paper into the empty bottle.  Then a shelled, moistened hard-boiled egg is placed on the mouth of the bottle.  The egg is clearly larger than the opening in the bottle.  The air inside the bottle begins to heat up and subsequently expands.  It is easy to notice the egg dancing around a bit as the air inside the bottle escapes around it.

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