1. Center of Gravity
Chapter 10

2. Center of Gravity Object’s average position of weight
For symmetrical objects of uniform density, CG is located at geometric center
May be located outside of oddly shaped objects
Objects rotate about their center of gravity

3. Center of Gravity
All the weight of an object appears to be located at center of gravity
For projectiles, center of gravity moves in parabolic path.
Even for exploding objects, center of gravity continues unchanged.

4. Center of Mass For nearly all objects is the same as center of gravity
Average position of all mass in object
Systems of objects rotate about center of mass: solar system center of mass not at center of sun so it wobbles as planets revolve

5. Locating Center of Gravity
For suspended objects, CG is directly beneath suspension point.
To find CG, suspend object from several points, draw vertical line down from suspension point each time
Intersection of lines is CG

6. Toppling Objects topple (tip over) when CG is beyond supporting base
Example: Leaning Tower of Pisa
Large base helps support objects
Important for rocket launches

7. Stability Depends on location of CG
Stable equilibrium: any displacement will raise CG of object--cone balanced on base
Unstable equilibrium: any displacement will lower CG of object--cone on tip
Neutral equilibrium: displacement will not change level of CG--cone on side

8. Stability
If CG is below suspension point, object is in stable equilibrium
Tall buildings have CG below ground level
Light objects rise to the surface because CG is lowered
Larger objects also rise because CG will be lower if smaller, denser material is below.

9. Center of Gravity of People
Person’s CG depends on body shape
Can be changed by changing position of arms, legs.
Important in dance, gymnastics, diving, etc.
Spreading feet apart widens base, increases stability.

10. Vocabulary Center of gravity Center of mass Neutral equilibrium
Stable equilibrium
Unstable Equilibrium