Question

A machine has an efficiency of 15%, If the energy input is 300 joules, how much useful energy is generated?
answers:
255 joules
285 joules
20 joules
45 joules

Answer 1

To find the useful energy generated by the machine, you can use the formula for efficiency:

\[
\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Energy Input}} \times 100
\]

In this case, the efficiency is 15% and the energy input is 300 joules. Rearranging the formula to find the useful energy output:

\[
\text{Useful Energy Output} = \text{Efficiency} \times \text{Energy Input} / 100
\]

Substituting the values:

\[
\text{Useful Energy Output} = 15\% \times 300 \, \text{joules} / 100
\]

\[
\text{Useful Energy Output} = 0.15 \times 300 = 45 \, \text{joules}
\]

So, the useful energy generated is **45 joules**.