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Beginner's Guide to Propulsion
Air Pressure

If so instructed by your teacher, print out a worksheet page for these problems.


  • Empty pop can
  • Bucket
  • Bunsen burner or other heat source for boiling water
  • Ice water
  • Matches
  • Beaker tongs

 Before you begin: Remember to record all observations. [Note the specific condition of the pop can before the boiling procedure (at room temperature), during the boiling step, and after the can is immersed in ice water.]


  1. In the pop can, place only enough water to cover the bottom of the can--approximately 5 mm.

  2. Holding the can with the beaker tongs over the Bunsen burner, bring the water in the can to a boil. Let boil for 2 minutes. Remember to record observations.

  3. Quickly invert the pop can in the ice water so that only the opened end is slightly submerged. Record your observations and discuss observations with your lab group.

  4. Sketch a diagram of the air pressure forces acting on the can in each of the following situations:
    A. Pop can at room temperature
    B. Pop can during boiling step
    C. Pop can a moment after it is immersed in the ice water.

    Note: A larger arrow should symbolize a larger force than a smaller arrow. 

  5. Explain how air pressure changed in the pop can during the procedure. To help with this question click on the slide Air Pressure for review in the Beginner's Guide to Propulsion. ----Is the pop can empty?

  6. Now click engine pressure ratio (EPR) to note changes in air pressure.
    A. What happens to air pressure as air travels through the engine from stations 0 to 8?
    B. How does molecular motion change from stations 0 to 8?
    C. What is one function of a gas turbine engine?

  7. After studying air pressure and gas turbine engines, list three questions that you or you and your lab partners have about this topic. 

Related Pages:
Propulsion Activity Index
Propulsion Index


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Editor: Tom Benson
NASA Official: Tom Benson
Last Updated: Thu, Jun 12 04:39:33 PM EDT 2014

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