Material:Shop Vac or any vac with a hose for suction (keep the vac under 5 horse power)39 gallon or larger plastic garbage bags (I have found janitors who were able to supply 55 gallon plus bags.) |
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Procedure:1. Have a student climb into the plastic bag and sit down so the bag is up around their neck, but never over their head.2. now place the open hose in the bag and ask the student to hold the end. Next bring the bag together at the opening and form as good of seal as possible. The student most understand that when the vac is turned on, they must keep the end open while keeping both the bag and their clothing from being sucked into the opening. (If the bag does not collapse around the student, it usually means they have allowed the opening to become covered.) Note: As the bag collapses around the student, it can be very revealing, so do not do this standing up. Rather have the pressure create a ball of the student. Also remember to turn off the vac when the student is well "Vacuum Sealed. If holes form in the bag, simply cover them with duct tape and bag another student. |
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| Understandings:
As the bag collapses, having part of the air inside the bag removed, the student will start to experience atmospheric pressure pushing in on them.
Background: The ideas that the atmosphere has mass and applies pressure is very difficult for younger students to understand. By removing a portion of this pressure, a student can experience a little of atmospheric pressure first hand. A fun extension of upper level classes would be to have students actually calculate the force being applied by the vac. Final Note: I have seen a teacher bring in a long metal rod that is one inch by one inch and has a total mass of 14.7 pounds, just so they can actually experience the mass that is pushing down on every square inch of their body (at sea level). Comments from Joe Stephen's Misconception book.Some representive student misconceptions related to air pressure1. Many students believe that blowing on something always makes it move away. 2. Some students believe that blowing takes the pressure with it. 3. For many young learners, air neither has mass nor can it occupy space. 4. Many children have difficulty making the connection between paper airplanes and jet airplane flight. Source of confusion and misconception 1. The explanations about the behavior of air and air pressure are difficult to visualize because air is usually invisible. 2. Many textbook presentations begin with abstrat concepts and terminology. 3.Classroom presentations usually ignore student's prior views and ideas. Grade Level:7 - 12Concepts:Air Pressure |
