Question

a machine has an efficiency of 15%. if the energy input is 300 joules, how much useful energy is generated? (1 point) 255 joules 45 joules 20 joules 285 joules

Explanation:

Step1: Recall the efficiency formula

Efficiency = $\frac{\text{Useful energy output}}{\text{Energy input}}\times100\%$. Rearranging for useful energy output gives $\text{Useful energy output}=\frac{\text{Efficiency}\times\text{Energy input}}{100}$.

Step2: Substitute the given values

Given efficiency = 15% and energy input = 300 joules. Then $\text{Useful energy output}=\frac{15\times300}{100}$.
Calculate $15\times300 = 4500$, and $\frac{4500}{100}=45$.

Answer:

45 joules