Center of Gravity

Challenge:Leg Lift

Stable vs. Unstable

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

Unstable Structures

• A structure may collapse if the external forces causes the structure to become unbalanced

• Also known as an “unbalanced” structure

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

Build on FIRM FOUNDATION!!!

Leaning Tower of Pisa

Class Challenge:Super Glue Chair

Center of Gravity

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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

Mass vs. Weight

• Mass

• Amount of matter in an object

• Weight

• Force of gravity felt on that object

What is “equilibrium”

A state in which opposing forces or influences are balanced in a “system”

A state of physical balance

What is a “system”

A structure made up of parts all related to one another

Challenge:The Impossible Leap

Ways to Increase Stability

• Lower the center of gravity = widening structure

• Increase speed (bike)

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Ruler Experiment

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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