Machines that change climate: Porsche 911 Turbo vs. Toyota Prius

Kevin Harrison, McDaniel College
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This activity shows students that decisions they make can significantly alter the amount of greenhouse gases they release to the environment. Students make back-of-the-envelope calculations to estimate the amount of carbon dioxide released to the environment by different autos. The students also learn about exponential growth by calculating how the money saved by purchasing an inexpensive car can be invested to great advantage.

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Learning Goals

  • To have students do back-of-the-envelope calculations.
  • To have students calculate exponential growth.
  • To allow students to explore the environmental and economic implications associated with transportation choices.
  • To help students gain a sense of the magnitude of the enormous mass of carbon dioxide emitted by automobiles.

Context for Use

The exercise is designed for a class consisting of non-science majors to illustrate important concepts for understanding global warming. It can be modified for higher-level courses and adapted to other courses related to global change. The activity is a homework problem that will take about 40 minutes. The students should be exposed to similar calculations in class.

Description and Teaching Materials

Activity Description (Microsoft Word 22kB Jun29 05)

Teaching Notes and Tips

Teaching Notes (Microsoft Word 28kB Jun29 05)
  • Teaching suggestions
  • Additional directions for discussion
  • Related problems and resources


Solution Set (Microsoft Word 22kB Jun29 05)

References and Resources

Fuel - mpg ratings, emissions information, scorecards and calculators

Web site for unit conversions:

Glover, Thomas J., Pocket Ref, Sequoia Publishing, 2002.
Harte, Consider a Spherical Cow, University Science Books.