Center of Gravity (COG) Definition--The Point located at an
object’s average position of the weight In other words…. The center of an
object’s weight Symmetrical object’s, like a baseball
the C of G would be in the exact center of object However other oddly shaped objects will
find COG in any number of positions, depending on weight distribution
COG
C.O.G. When objects rotate freely they must
rotate about an axis through the COG
Basically treat the object as if all its weight is concentrated at that one pt.
In class demos…
C.O.G. --Balancing For an object to balance,
and not topple… support must be directly below C.O.G.
Where C.O.G. is located Generally found in the
middle of all the weight… Does not even have to be
within, the object itself Ex. boomerang
Will be located toward one side of an object where most of its mass is focused… Ex. Weebles
COG
gravity
Weebles Wobble, but they don’t fall down??? Weebles have very low COG Whenever rolling it will roll to a
stop when its COG is as low as possible This occurs when it is standing upright Also occurs for inflatable toy clowns
Objects with a low COG are less likely to topple because of this principle
Higher COG is, the easier to topple
Balancing Stuff Again, all that has to happen to
balance, is for a support to be directly beneath COG
Advantages of low COG Athletic advantages
wrestling—harder to takedown
Football Both easier to drive power
through their legs SUV’s …. Tip over all the
time b/c COG is too high SUV Farmer’s tractors
Much more control in all vehicles w/ low COG
Animals
Low COG High COG Low COG High COG
Humans - Where is our COG? Just below our belly
button Notice, support
always below COG Bipedalism??
Only mammals w/ this ability to walk on 2 legs
Because of Evolution and how our legs changed to balance between steps is why we are only mammals to walk
Robots – Where is the COG?
Where is this robot’s Gravity “Average Mass” Centered?
A
B
C
Robots – Center of Gravity
Is this robot’s gravity more centered at it’s starting point “A,” or in it’s current position, “B?”
How do you know?
AB
Robots – Center of Gravity
How has the builder of this robot considered centering the gravity for the task that it has to accomplish?