Determine how much the object weighs. Make sure to calculate any added weight to the object. For example, assume a seesaw 14 feet long that weighs 40 pounds and has two people sitting on it, one weighing 50 pounds and the other 70 pounds. Both of these people are sitting 1 foot from the edge of the seesaw.
Calculate the center of gravity for each object in the example. The equation for the center of gravity is cg = center of gravity, x = distance from a reference point, and m = mass of an object is: cg = ((m1 * x1) + (m2 * x2))/ (m1 + m2). The reference point in this example is one end of the seesaw, although it can be anywhere on the seesaw. The seesaw's center is 7 feet from the reference point. Person A is 13 feet away from the reference point and Person B is 1 foot away from this point. The center of gravity for each object equals: 40 pounds x 7 feet = 280; 50 pounds x 1 foot = 50 foot-pounds; 70 pounds x 13 feet = 910 foot-pounds.
Add the sum of all the equations in Step 2, and the result is 1,240 foot-pounds. The weights added together: 40 pounds + 50 pounds + 70 pounds = 160. Divide the sum of the centers of gravity by the sum of the weights: 1,240 foot-pounds/ 160 pounds = 7.75 feet. This is the center of gravity of the seesaw from the reference point.