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Principles of Stability. 1. Build on a firm foundation 2. Balance forces 3. Keep thrust lines vertical 4. Use rapid rotation.

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Presentation on theme: "Principles of Stability. 1. Build on a firm foundation 2. Balance forces 3. Keep thrust lines vertical 4. Use rapid rotation."— Presentation transcript:

1 Principles of Stability

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3 1. Build on a firm foundation 2. Balance forces 3. Keep thrust lines vertical 4. Use rapid rotation

4 Thrust Lines Student example

5 Principle #1: Build on a firm foundation Build on stable, solid ground Beware of climactic changes (melting, freezing, runoff water) Erosion

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7 Principle #2: Balance forces Forces are balanced if they are... equal in size opposite in direction pointing along the same straight line

8 Balance Force: Counter Weights Mass that balances another mass Pulls in an opposite direction to a dangerous force Structure must withstand tension

9 Balance Force: Guy Wires Mass that balances another mass Pulls in an opposite direction to a dangerous force Structure must withstand tension

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11 Principle #3: Keep thrust lines vertical Problem: Center of gravity is not directly over structure = pushes outward/inward on supports (ie: think table) Solution: distribute weight towards supports Keeping thrust lines vertical

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13 Principle #3: Keep thrust lines vertical Half-circle Arches distribute weight straight down cannot span a large space

14 Principle #3: Keep thrust lines vertical Buttresses distribute weight straight down AND to the supporting buttresses can build bigger and heavier

15 Principle #3: Keep thrust lines vertical Trusses arches with their ends tied together by a strong beam Outward force on beam is balanced by the inward tension force

16 Principle #4: Use rapid rotation The faster the spin the more stable If most of the mass of a wheel is located far from the center, the greater the stability Think... riding a bicycle football spiral

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18 Stable or Unstable?

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26 Experiment 1: Balancing Act 1. In groups of 2, gather materials (2 worksheets per person) 2. Roles 1. Subject - person doing experiment (balancing act) 1. ***on one foot*** (you can do both feet if it is too difficult) 2. Observer/Recorder - timer for each trial, records performance of subject 3. Switch

27 To Do Complete your Principles of Stability graphic organizer (*with description and colored drawing of an example)

28 Paper Tower Challenge

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