# Efficiency of a Machine

What is the energy input and the useful work output of a machine that has an efficiency of 90%?

Your answer is Energy input = 100%, Useful work output = 90%

## Understanding Machine Efficiency

Machine efficiency is a measure of how well a machine converts energy input into useful work output. In this case, if a machine has an efficiency of 90%, it means that 90% of the energy input is converted into useful work output. Therefore, the energy input is considered to be 100% and the useful work output is 90%.

Efficiency can be calculated using the formula:

**Efficiency = (Useful work output / Energy input) x 100%**

So, for a machine with an efficiency of 90%, the energy input is 100% and the useful work output is 90%. This means that 90% of the energy input is converted into useful work output, resulting in an efficiency of 90%.