What is the resistance arm?

• A. The distance between the resistance and the fulcrum
• B. The distance between the applied force and the fulcrum
• C. The perpendicular distance between the resistance force and the fulcrum
• D. The distance from the fulcrum to the line of action of the applied force

Answer: (A)

In a lever, torque about the fulcrum depends on how far the force is from the pivot. The resistance arm is the distance from the fulcrum to where the load (the resistance) acts on the lever. This distance sets how much torque the load can produce for a given resistance force, and it’s the direct measure of the lever’s resistance arm. The other descriptions point to the effort arm (distance from the fulcrum to where the applied force acts), or to the moment-arm concepts related to the line of action of the forces, but the resistance arm specifically refers to the distance between the fulcrum and the point of resistance.