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Center of Gravity
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Challenge:Leg Lift
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Stable vs. Unstable
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Stable Structures
• The forces of gravity acts on all parts of the structure
• All parts are evenly distributed around the center of gravity
• = the structure is stable
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Unstable Structures
• A structure may collapse if the external forces causes the structure to become unbalanced
• Also known as an “unbalanced” structure
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Firm Foundation
• The foundation must be stable.
• If not, compressive forces may cause structure to tip and become unstable.
• Soil type and formations critically important in building planning
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Build on FIRM FOUNDATION!!!
Leaning Tower of Pisa
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Class Challenge:Super Glue Chair
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Center of Gravity
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QuickTime™ and a decompressor
are needed to see this picture.
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What is center of gravity?
• The center of gravity is the specific point where all of the mass of the structure is evenly distributed around
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Mass vs. Weight
• Mass
• Amount of matter in an object
• Weight
• Force of gravity felt on that object
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What is “equilibrium”
A state in which opposing forces or influences are balanced in a “system”
A state of physical balance
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What is a “system”
A structure made up of parts all related to one another
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Challenge:The Impossible Leap
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Ways to Increase Stability
• Lower the center of gravity = widening structure
• Increase speed (bike)
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QuickTime™ and a decompressor
are needed to see this picture.
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Ruler Experiment
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Experiment: Spoon & Fork
Steps
1. Hand in your graphic organizer.
2. In partners of 2, get a spoon, fork, toothpick and a beaker
3. Put fork and spoon together
4. Add toothpick
5. Find center of gravity by balancing on table
• *Bonus* - break off toothpick where center of gravity is
6. Draw your “system” and label. Include center of gravity, equilibrium line. Explain why the “system” is balanced (ie: why is it balancing?)
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QuickTime™ and a decompressor
are needed to see this picture.
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