Which formula relates center of gravity to weight and moment?

• A. CG = Weight × Moment
• B. CG = Weight / Moment
• C. CG = Moment / Weight
• D. CG = Moment × Weight

Answer: (C)

The center of gravity is the point at which the aircraft’s total weight can be considered to act, found by taking a weighted average of all locations of weight. Each item contributes a moment equal to its weight multiplied by its distance from the datum, and the overall CG is the total moment divided by the total weight. So the relationship is CG = Moment / Weight.

For example, if the total moment is 100,000 in-lbs and the total weight is 2,000 lbs, the CG is 50 inches aft of the datum. The other forms would not give a distance: multiplying weight by moment yields a product with incompatible units, dividing weight by moment gives an illogical unit, and multiplying moment by weight again isn’t a usable distance either.