Mat held down by atmospheric pressure.

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The atmoshperic mat consists of a 10.5” square sheet of Neoprene that lays flat and does not allow air between it and the surface below. Given that atmospheric pressure at sea level is approximately 14.7 lb/in2, the mat theoretically experiences 1620 lbs of pressure. This makes it near impossible to pull the mat off the table by pulling straight up on the hook. However, by peeling the mat off the table, the air creates equal pressure on both sides of the mat allowing it be easily removed. Obviously, due to imperfections in the rubber and the presence of air (particularly under the hook), one requires far less than 1600 pounds of force to lift the sheet. A force transducer or a spring scale can be attached to the hook if you want to show the class how much force is exerted.
UCB Index: 
C+30+62
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Comments

Mr. Little

Tue, 10/06/2015 - 16:03

Let participants handle the mat so they can see how light it is then demonstrate the demo and show how hard it is to lift; this can create a discussion about what is holding the mat down. Note that the surface you put the mat on must be very flat indeed. It won't function at all on asphalt or other rough surfaces. As always when you present a demo make sure you ask the participants questions before you demonstrate and after. Think about the concepts involved beforehand; having a friend ask you questions about it can be very revealing as to if you understand it well or not. Whenever you ask a question count to five (or at least three) in your head waiting for an answer before you stay anything else.