2-3 its arm is negative or –60 inches. The new arm of weight B is  20 inches (110 – 90), and it is also to the left of the datum, so  it is –20; the new arm of weight C is 40 inches (150 – 110).  It is to the right of the datum and is therefore positive.  determine the balance point by making a chart like the one  in  Figure 2-4 . The lever is balanced when the sum of the moments is zero.  The location of the datum used for determining the arms of  the weights is not important; it may be in various locations,  but all of the measurements must be made from the same  datum location. As noted in  Figure 2-4 , A weighs 100 pounds and is 50 inches  from the datum; B weighs 100 pounds and is 90 inches from  the datum; C weighs 200 pounds and is 150 inches from the  datum. The total of the weights is 400 pounds, and the total  moment is 44,000 lb-in. The procedure for  fi nding the balance point is the same  anywhere the datum is located. In  Figure 2-7,  the datum is  located at C. Weight A has an arm of –100 inches (negative  because it is to the left) of the datum and weight B has an  arm of –60 inches from the datum. The table in  Figure 2-8 is used to determine the new balance point. Determine the balance point by dividing the total moment  by the total weight. A balance point is equal to the CG and  can be mathematically written as: To prove this is the correct balance, move the datum to a  location 110 inches to the right of the original datum and  determine the arm of each weight from this new datum. [Figure 2-5]  Then, make a new chart similar to the one in  Figure 2-6 . If the balance point is correct, the sum of the  moments is zero. To verify that this is the correct balance point, move the datum  40 inches to the left of the original datum and determine the  arm of each weight from this new datum as in  Figure 2-9 . The new arm of weight A is 60 inches (the difference between  110 and 50), and since this weight is to the left of the datum,  Figure 2-9.  Locating balance point with datum left of original. Figure 2-6.  Proving balance point with three weights is correct. Figure 2-5.  Locating balance point. Figure 2-8.  Determining new balance point. Figure 2-7.  Locating balance point with datum at C. Figure 2-4.  Finding balance point with datum located off the lever. CG =  total moment total weight C = 200 A = 100 B = 100 −20 −60 110 +40 CG Original datum New datum Item Weight (lb) Arm (in) Moment CG 5,000 9,000 30,000 44,000 110 Weight A Weight B Weight C 100 100 200 400 50 90 150 Item Weight (lb) Arm (in) Moment (lb-in) −6,000 −2,000 +8,000 0 Weight A Weight B Weight C 100 100 200 −60 −20 +40 C = 200 A = 100 B = 100 −40 Datum −20 −60 +40 C = 200 A = 100 B = 100 −60 −100 Datum Item Weight (lb) Arm (in) Moment CG −10,000 −6,000 0 −16,000 −40 Weight A Weight B Weight C 100 100 200 400 −100 −60