Question

1. a windmill converts 35,000 j of wind energy into electricity. how efficient is the windmill if the wind has 45,000 j of kinetic energy? round to the nearest percent. 76% 77% 78% 77.8%

Explanation:

Step1: Recall efficiency formula

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

Step2: Identify input and output energy

The input energy (kinetic energy of wind) is $E_{in} = 45000\ J$ and the useful output energy (electrical energy) is $E_{out}=35000\ J$

Step3: Calculate efficiency

$\eta=\frac{35000}{45000}\times 100\%=\frac{3500000}{45000}\% \approx 77.8\%$

Answer:

$77.8\%$