# Principles of Stability

## Presentation on theme: "Principles of Stability"— Presentation transcript:

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