If the fulcrum is centered, how much force is needed to lift a 10-pound object?

• A. 5 pounds
• B. 10 pounds
• C. 15 pounds
• D. 20 pounds

Answer: (B)

Torque is the turning effect of a force, calculated as force times distance from the fulcrum. If the fulcrum is centered, the lever arms on both sides are equal. The weight on one side creates a torque of 10 pounds times that same arm length. To produce an equal and opposite torque, your push must have the same force: 10 pounds. So, in an ideal, frictionless lever, 10 pounds of force is just enough to lift the 10-pound object. In real life, friction may require a touch more, but the baseline answer is 10 pounds.