one class period
You may print this activity
for educational use.
Before their visit, students will learn to ... stick to a surface
like a giant squid sucker. How a sucker works by making a
At sea level the atmosphere presses down on objects at 14.7 pounds per square inch of pressure. In the ocean, water presses down on objects with even more pressure. The deeper you go, the greater the pressure. Where giant squid roam, water pressures can reach thousands of pounds per square inch.
Water pressure helps a giant squid attach its suckers onto objects, like the skin of prey or its predator, the sperm whale. When a giant squid first places its sucker on a whale's skin, the water pressure inside the sucker is the same as it is outside the
sucker. But then the giant squid seals off the outer edge of the sucker and pulls the center of the sucker away from the whale. This creates a kind of vacuum: the water pressure inside the sucker becomes much less than that outside of it. Higher water pressure outside the sucker keeps the sucker attached, as long as the seal stays intact.
This activity gives your students a closer look at how giant squid suckers work. Keep in mind that you're using air pressure instead of water pressure to create the suction. But the principle is the same.
- A plumber's suction cup.
- A smooth surface, such as a plastic table top.
- A pin.
QUESTIONS TO BEGIN
How do you hold onto objects?
How would you hold on if you couldn't use your fingers?
- Moisten the suction cup and the surface on which it is to be placed.
- Have a student press the cup down on the smooth surface, then try to pull it away.
- Place a small hole in the suction cup. Repeat steps 1 and 2. It should be easy to pull the cup away from the table top.
- Have a student hold a finger over the hole on the next try.
- It should be difficult, if not impossible, to pull the cup from the surface.
- Explain that although we don't notice it, the atmosphere pushes down at about 14.7 pounds per square inch. If the suction cup encloses an area of 16 square inches, the force required to pull it loose from the smooth surface could be more than 200 poun
ds. This represents the pressure of the atmosphere on the top of the rubber cup. Under water, a giant squid uses the pressure of the water to help it stick tight to food it catches.
QUESTIONS TO CLOSE
How does a giant squid hold on to something?
How do suction cups compare to fingers in how well they hold on?
Brown, R. J. 333 More Science Tricks and Experiments. Blue Ridge Summit, PA, Tab Books, 1984.
Vivian, C. Science Experiments and Amusements for Children. New York, Dover Publications, Inc., 1963.
Gates, Phil. Nature Got There First: Inventions inspired by nature. New York: Kingfisher, 1995.