an engine has an energy input of 125 j, and 35 j of that energy is transformed into useful energy. what is…

Explanation:

Step1: Recall efficiency formula

Efficiency $\eta=\frac{\text{useful energy output}}{\text{total energy input}}\times100%$

Step2: Substitute values

Given useful energy output $E_{out}=35\ J$ and total energy input $E_{in}=125\ J$. So $\eta=\frac{35}{125}\times 100%$

Step3: Calculate

$\frac{35}{125}\times100% = 0.28\times100%=28%$

Answer:

A. 28%