In a lever system, which component is the axis about which rotation occurs?

• A. An axis or fulcrum that the lever rotates about
• B. A rigid object that creates the lever
• C. A force or effort that is applied
• D. A resistance or load that is overcome

Answer: (A)

Rotation of a lever happens around a fixed pivot point called the fulcrum, which is the axis of rotation. This pivot stays in place while the lever swings, so the effort and the load create torques around that point to produce movement. The lever itself is just the rigid bar, the effort is the input force, and the load is the resistance to overcome; none of these are the axis about which rotation occurs. So the axis or fulcrum is the correct concept.