Math in the News: 10/17/11
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Transcript of Math in the News: 10/17/11
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10/17/11
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Washington Monument• On August 23, 2011,
an earthquake of magnitude 5.8 struck Virginia. The epicenter of the earthquake was over 80 miles from Washington, DC.
• Yet, the Washington Monument sustained a good deal of damage.
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Washington Monument• This video shows two
security cameras within the Washington Monument both before and during the earthquake. Note the extensive amount of damage to the interior.
• http://www.nps.gov/wamo/photosmultimedia/videos.htm
• Click on “500 ft level Video 1st View” and “2nd View.”
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Washington Monument• Why would the
Washington Monument be so affected by the earthquake, while most buildings were not?
• Let’s investigate the geometry of the Monument using paper, pencil, straightedge, and compass.
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Scale Model of the Washington Monument
Draw a horizontal line.
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Scale Model of the Washington Monument
Mark off a length of 55 units.
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Scale Model of the Washington Monument
Construct the perpendicular bisector of the 55-unit segment. Use the compass to construct the bisector.
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Scale Model of the Washington Monument
Mark the vertical height of 550 units.
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Scale Model of the Washington Monument
From the top point, mark a vertical length of 55.5 units.
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Scale Model of the Washington Monument
Construct the horizontal segment shown.
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Scale Model of the Washington Monument
Construct the horizontal segment shown.
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Scale Model of the Washington Monument
Create the outline of the monument.
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Scale Model of the Washington Monument
You now have a scale model of the Washington Monument.
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Washington Monument• The shaking from the
earthquake makes the whole monument vibrate, but the strongest impact is felt at the monument’s center of gravity.
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Scale Model of the Washington Monument
Because the Monument has vertical symmetry, you can easily locate the center of gravity by connecting the midpoints of the vertical sides.
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Washington Monument• The Washington
Monument was not designed to withstand earthquakes. Given that it is a rigid stone structure, even minor vibrations will create cracks in the stone.
• We would expect more damage near the center of gravity.
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Washington Monument• Watch this helmet cam
video of the workers rappelling the side of the Monument. Note where the cracks are located.
• http://www.nps.gov/wamo/photosmultimedia/videos.htm
• Click on “Helmet Cam.”