Weight X arm=moment. From the pivot point on a teeter toter 10 lbs at ten feet = 100 moments. 50 lbs at 20 feet = 100 moments. They balance. "Positive and negative moments." The pivot point on full size planes is called the reference datum point and is located near the nose so that all moments will be positive to allow use of tech manuals for cg computation.Moment arm in purest terms is the distance from the pivot point to the weight or applied force,pressure.
CAZ