Tae Kwan Do Discrepant Event |
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Authors: Laurie Aiello and Troy Labnow | Discrepant Event
- Teacher's Guide SED 695B; Fall 2005 |
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Detailed Explanation of Discrepant
Event |
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Principles Illustrated:
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Materials:
Procedure:
Results:
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Standards Addressed: 8 th GRADE PHYSICAL SCIENCE PHYSICS |
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Questioning Script Prior Knowledge & Experience: Root Question: Target Response: Common Misconceptions:
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Here is a good way to begin the demonstration. Show the students how easy it is to lift the newspaper with the stick. If the stick is lifted slowly, air has plenty of time to get under the newspaper, equalizing the pressure on both sides, so that the only weight you must lift is that of the newspaper. |
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Here a stack of books weighing 20 lbs is quite obvious to the students that the stick will break if you apply pressure to the end of it. | |||
If the newspaper is lifted quickly, air has little time to move underneath so that you are moving not only the newspaper but the column of air above the paper as well since there is no compensating pressure underneath. The result is that with a quick (little time) force (a hard karate chop) illustrates impulse. Less time and a lot of force breaks the stick. |
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The rapid acceleration of the paper when the stick is struck attempts to accelerate the column of air above the newspaper. Here the students can calculate the area of the newspaper and relate it to the pressure of the air on the newspaper. Pressure = force over area P = F/A. Air pressure is 14.7 psi and the area of an average newspaper in 575 sq inches. That is a total of 8450 lbs or about 4.22 tons of force on the newspaper. |
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References & Links: Science and Mathematics Initiative for Learning Enhancement SMILE University of Illinois "Atmospheric Pressure" Wikipedia's definition of "Impulse" Glenbrook South Physics Page "Inertia"
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