In the theory of weight and balance, what is the name of the distance from the fulcrum to an object?

• A. Lever arm
• B. Momentum
• C. Radius
• D. Arm length

Answer: (A)

In weight and balance, the turning effect of a weight about the pivot depends on how far the weight is from the fulcrum. That distance, used to calculate the moment (or torque), is called the lever arm. The lever arm is the perpendicular distance from the fulcrum to the line of action of the weight, and the moment equals the weight times this distance.

Momentum is about motion (mass times velocity), which isn’t the distance used here. Radius is a general distance from the center to a point and isn’t the standard term for this purpose. Arm length is a casual description and not the technical term used in weight-and-balance calculations. The precise term that fits the context is lever arm.