Water Pressure

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Author: Janice VanCleave

So You Want to Do a Project about "Water Pressure!


To determine a way to measure water pressure.


  • Sharpened pencil
  • 9-ounce (270-mL) paper cup
  • Ruler
  • Masking tape
  • 2-quart (2-L) pitcher
  • Tap water
  • 2 metal spoons
  • Helper


  1. Use the pencil to punch two holes of similar diameter in one side of the cup. Make one hole 3 inches (7.5 cm) from the bottom of the cup and the other hole 1 inch (2.5 cm) from the bottom and slightly to the left or right of the top hole.
  2. Place a strip of masking tape over the holes on the outside of the cup.
  3. Fill the cup and the pitcher with water.
  4. Set the cup on the edge of a sink. Secure the cup to the counter with tape.
  5. Remove the tape from over the holes in the cup, and ask your helper to keep the cup filled by pouring water from the pitcher into the cup.
  6. Observe the distance each stream of water squirts out its hole in the cup.
  7. Use the spoons to mark the spots where the water streams hit the bottom of the sink.
  8. Use the ruler to measure the distance from each spoon to the side of the sink. These are the distances of the water streams. Record the distances in a Pressure Data table like the one shown.



Streams of water squirt out the holes in the cup. The lower stream squirts farther.


Pressure is a force applied over an area. Since water has weight, it exerts pressure. One factor that affects the amount of pressure exerted by water is its depth. The pressure of water increases with depth because of the weight of the water pushing down from above. The greater the pressure, the farther the stream of water squirts, so the stream of water coming from the bottom hole squirts farther. In the ocean, the deeper you go, the greater the pressure of the water pushing down on you. For every 33 feet (10 m) you go down, the pressure increases by 15 pounds per square inch (1.1 kg per cm2). In some of the deepest parts of the ocean, the pressure is as great as an elephant's weight pressing down on an area the size of a postage stamp.

For Further Investigation

If the hole was bigger, would the stream go as far? A project question might be, How does the size of an opening in a water container affect the pressure of released water?

Clues for Your Investigation

  1. Repeat the experiment, using three cups and making a different size hole in each-one large, one medium, and one small.
  2. Take photographs of the water streams from the cups with different size holes and display them to illustrate your results. Diagrams of the squirting water with labels for the distance between the streams can also be used as part of a project display.


References and Project Books

Ganeri, Anita. The Usborne Book of Ocean Facts. London: Usborne, 1990.

Glover, David. Flying and Floating. New York: Kingfisher Books, 1993.

National Wildlife Federation. Ranger Rick's Naturescope Guides: Diving into Oceans. Washington, D.C: National Wildlife Federation, 1992.

Pernetta, John. Atlas of the Oceans. Chicago: Rand McNally, 1994.

Vecchione, Glen. 100 First-Prize Make-It-Yourself Science Fair Projects. New York: Sterling, 1999.

VanCleave, Janice.janice VanCleave's Guide to the Best Science Fair Projects. New York: Wiley, 1997.

  • Janice VanCleave's Oceans for Every Kid. New York: Wiley, 1996.

Walpole, Brenda. 175 Science Experiments to Amuse and Amaze Your Friends. New York: Random House, 1988.

Wells, Susan. The Illustrated World of Oceans. New York: Simon & Schuster, 1991.

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