Center of Gravity
   

The center of gravity of any object is a special point.

  1. If the object is in free fall, the CG is the point around which it will rotate. The CG will travel in the same path that a point particle (e.g. a small ball) would have traveled.
  2. The CG is the balance point: if supported from below by a single point under the CG, the object will be precariously balanced. If supported by a broad area (the "base of support"), the object will be stable as long as the CG is over the base of support.
  3. If supported from above by a single point, the CG will always hang directly under the suspension point.
  4. The work needed to lift a 3D object is given by Ug=mgh, where h is the height that the CG rises.

Examples

1. Standing on tiptoes, touching toes

2. Hummingbird toy

3. What does "top-heavy" mean?

4. Standing up

5. Pole Vaulting

6. Why wheels work

 

Activities & Practice
to do as you read

Watch these videos:

1. Liebherr excavator climbing a tower. This is somewhat lengthy (9 minutes) and slow. Feel free to skip forward.

2. Skills with a 15-ton Loader.

3. Extreme Maneuver: Unloading the Excavator

4. Epic Crane Fail

Additional Activities & Practice

1. Draw a dot where you think the CG is for each of these flat objects.

2. Find a map of any state, country or continent and print or trace it onto a piece of paper. Glue the map to a piece of thin cardboard and cut out the shape. Make it fairly big, at least 15 cm across. Find the CG, and tell me what city or town is closest.

  
   

 

  

 

HTML Comment Box is loading comments...