Question

1. an engine is 35% efficient. if it takes in 7,000 j of chemical energy from fuel how much useful mechanical energy does it produce?

Explanation:

Step1: Recall efficiency formula

Efficiency $\eta=\frac{W_{useful}}{Q_{input}}\times100\%$. We need to find $W_{useful}$, and we know $\eta = 35\%=0.35$ and $Q_{input}=7000\ J$.

Step2: Rearrange formula to solve for $W_{useful}$

$W_{useful}=\eta\times Q_{input}$.

Step3: Substitute values

$W_{useful}=0.35\times7000\ J = 2450\ J$.

Answer:

$2450\ J$