Which aspect of a simple machine is represented by the ratio of work output to work input?

• A. Efficiency
• B. Actual mechanical advantage
• C. Ideal mechanical advantage
• D. Power

Answer: (B)

The main idea here is efficiency: how well a simple machine turns the energy you put in into useful work. Efficiency is the ratio of useful work output to the total work input. In other words, how much of your input energy actually goes into doing the task, with the rest typically lost to things like friction, heat, or sound.

If you put in 100 joules of energy and get 80 joules of useful work out, the efficiency is 80/100 = 0.8, or 80%. The other options describe different concepts: actual mechanical advantage measures how much the machine multiplies force (output force divided by input force), ideal mechanical advantage uses distance ratios assuming no losses, and power is how fast work is done (work per unit time).