Environmental Science for AP* (2nd Edition)

Published by W. H. Freeman
ISBN 10: 1464108684
ISBN 13: 978-1-46410-868-6

Chapter 12 - Module 34 - Pattern of Energy Use - AP Review Questions - Page 408: 2


c) 580 MJ

Work Step by Step

We know how much energy a car uses per kilometer, and we want to find how much energy a car uses per person. We will be using dimensional analysis as well. Let's first determine how much energy is required to drive 1-mile using dimensional analysis, since the length of the car trip is in miles and not kilometers. We know that one mile is about 1.61 kilometers: $\frac{3.6 MJ}{1 km} * \frac{1.61 km}{1 mile} = \approx \frac{5.8 MJ}{1 mile}$ Now let's find the number total amount of energy needed to drive the 400-mile trip: $\frac{5.8 MJ}{1 mile} * 400 miles = 2,320 MJ$ Now let's find the amount of energy needed per person: $\frac{2,320 MJ}{4} = 580 MJ$
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