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Q & A: Experiments finding center of gravity

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Most recent answer: 10/30/2007
Q:
I am looking for an exiperment that would find an objects center of gravity, could you give me some suggestions? Please?
- jacquelyn (age 44)
Genesee Community College, East Bethany, NY
A:
The way we do it in lecture demonstrations is to let the object hang from a string which may be attached to the object in different places. Find the place where the string is supporting the object and continue the line that the string points in (straight down!). That line will go through the center of mass of the object. One line isn't enough, you'll have to turn the object a bit and hang it from a string attached somewhere else. The intersection of these two lines is at the center of mass of the object.

If the object is solid and three-dimensional, it may be hard to draw these lines and find their intersection. But then again, the center of mass is buried deep inside the object anyhow. If the object is two-dimensional, like a piece of cardboard (good for demonstrations), you can draw lines on the cardboard.

Tom

(published on 10/22/2007)

Follow-Up #1: Center of gravity of a billiard cue

Q:
How can I find the centre of gravity of a billiard cue please? Thanks
- Neil Bugeja (age 15)
Gzira, Malta
A:
The method described in the question/answer you are referring to is correct, but here is another quick and dirty method.  Hold your hands in front of you spaced about a meter apart with your two forefingers extended.  Have a friend place the cue on your two fingers.  Slowly bring your two hands together.   The cue will move slightly one way or the other.  When your hands are very close together the cue will have moved to its center of gravity.

LeeH

(published on 10/30/2007)

Follow-up on this answer.