Locating the Center of Gravity

To further our studies in Gravity, we built a structure, using a plumb line, to help us determine the center of gravity.

We chose a rectangular plate as our test object and first developed our own hypothesis as to where the center would be -  the red dot.

Next we suspended the rectangular plate by one of its corners directly under the plumb line.  We marked a vertical line along the plumb line.   Then we suspended the plate by another corner and marked another vertical line.  The intersection of the 2 lines demonstrate the center of gravity.

We wanted to see if the center of gravity changes if we change the object, so the kids attached some pieces to the rectangle and developed a new hypothesis.  They were quite surprised when they discovered that the center of gravity had shifted!

Technically we have just determined the "Center of Area" for the rectangular plate.  The true Center of Gravity is a three-dimensional point halfway through the plate at the spot of its center of area.

Center of Area  -  
The center of gravity projected onto the surface of an object.

Note:  Even though it's easy to build a contraption similar to this one from things around the house and do the experiment, for some of us busy homeschool moms it's just easier when it all comes in a kit.  The kids received this kit at Christmas time and it's been a life saver, making science fun and hands-on!

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