Principles of Stability
Principles of Stability Build on a firm foundation Balance forces Keep thrust lines vertical Use rapid rotation
Thrust Lines Student example
Principle #1: Build on a firm foundation Build on stable, solid ground Beware of climactic changes (melting, freezing, runoff water) Erosion
Principle #2: Balance forces Forces are balanced if they are... equal in size opposite in direction pointing along the same straight line
Balance Force: Counter Weights Mass that balances another mass Pulls in an opposite direction to a dangerous force Structure must withstand tension
Balance Force: Guy Wires Mass that balances another mass Pulls in an opposite direction to a dangerous force Structure must withstand tension
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
Principle #3: Keep thrust lines vertical Half-circle Arches distribute weight straight down cannot span a large space
Principle #3: Keep thrust lines vertical Buttresses distribute weight straight down AND to the supporting buttresses can build bigger and heavier
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
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
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Stable or Unstable?
Experiment 1: Balancing Act In groups of 2, gather materials (2 worksheets per person) Roles Subject - person doing experiment (balancing act) ***on one foot*** (you can do both feet if it is too difficult) Observer/Recorder - timer for each trial, records performance of subject Switch
To Do Complete your “Principles of Stability” graphic organizer (*with description and colored drawing of an example)
Paper Tower Challenge