In a basic lever system, what is the effect of using a longer input arm?

• A. There is no change in required force.
• B. You need more input force.
• C. You need less input force.
• D. It increases the load carried without changing force.

Answer: (C)

A longer input arm increases the lever’s mechanical advantage. The force you apply creates torque equal to input force times the input arm length. To balance and lift the same load, the torque from the input must match the torque from the load, which is the load force times the load arm length. Making the input arm longer boosts the torque you can generate for the same input force, so you can achieve the required balance with a smaller input force. In other words, you need less input force to lift the same load.

Keep in mind the trade-off: you must move the input through a longer distance to raise the load a given amount. This explains why leverage can reduce force but increase the distance moved.