What is the formula for mechanical advantage?

• A. Input force divided by output force
• B. Output work divided by input work
• C. Output force divided by input force
• D. Distance moved by input force divided by distance moved by output force

Answer: (C)

The main idea here is how many times the machine multiplies your effort into output force. The best way to capture that is the ratio of the output force to the input force: F_out divided by F_in. This shows exactly how much force you gain with the machine.

In an ideal machine, energy is conserved, so input work equals output work, which means F_out / F_in also equals input distance divided by output distance. That ties the force gain to how far you move the input versus the load. The other options don’t describe the gain in force: comparing output and input work isn’t the definition of mechanical advantage (it’s 1 in an ideal machine and drops with losses), and using the distance ratio alone describes velocity ratio rather than force multiplication.