A lever has an effort arm of 6 cm and a load arm of 3 cm. If the input force is 12 N, what is the load force at the end?

• A. 6 N
• B. 12 N
• C. 24 N
• D. 36 N

Answer: (C)

Mechanical advantage of a lever comes from the balance of moments: input force times its arm equals output force times the load arm. In an ideal lever, 12 N acting on a 6 cm effort arm must balance the load on a 3 cm load arm: 12 × 6 = F_load × 3. Solving gives F_load = (12 × 6) / 3 = 24 N. Since the effort arm is twice as long as the load arm, the lever multiplies the input force by two, so the load at the end is 24 N. This also shows why the other numbers aren’t correct: mixing up the arms or omitting the arm lengths changes the balance and leads to incorrect results like 6 N or 36 N.