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This
activity page will offer:
-
A hands-on experience in buoyancy
- An
observation of a working ballast tank
- An
operational definition of blowing ballast
MATERIALS
- 1-liter clear plastic beverage container
- Large balloon
- Rubber band
- Fishing weights
- Tape
- Aquarium tubing (rubber hose or a chain of plastic straws
with flexible necks will also work)
- Large tub or tank
PROCEDURE
- Stretch a balloon by inflating and deflating it about
a dozen times. If necessary, pull and stretch out the balloon
to make it more flexible.
- Obtain a length of plastic aquarium tubing. If you do
not have tubing, you can construct such a tube by connecting
straws. If you are using straws, secure them with waterproof,
sturdy tape, and make sure to place a bend in the straw
as shown above.
- Place the mouth of the balloon over one end of the straw/tubing.
Use a rubber band to secure the balloon to the straw/tube
end. Make sure that the rubber band does not squeeze off
the air passage.
- Insert the balloon into the 1-liter clear plastic beverage
container.
- Place the container in a large tank or tub of water. Let
the container fill with water. As it fills with water, the
container should sink. If it does not sink, add several
fishing weights until the water-filled container settles
to the bottom of the tank.
- Make a prediction. Suppose you blew a small puff of air
into the balloon. How would that change the buoyancy of
your "submersible"?
- Suppose you inflated the balloon to a greater volume?
Would that offset the sub's weight?
Questions
- Why was it necessary to "pre-stretch" the balloon?
- Why was it important to keep the air passageway unblocked?
- What was the purpose of the fishing weights?
- What happened when you blew into the open end of the straw/tube?
- Consider the balance of forces that are responsible for
the surfacing and diving of your classroom submersible.
How can you apply what you've learned to Alvin's operation?
EXTENSIONS
A Biological Connection
Some
species of seaweed have tiny air bladders that line their
stem-like parts. Think about it. What survival advantage might
these sacs of air offer?
Historical
Fiction
Historical
fiction is a writing style that is based upon the blend of
historical events and fictional characters or exchanges. Can
you image what it would have been like to be lowered down
in a bathysphere, like William Beebe? In 1930, this four-foot-in-diameter
steel sphere was the first to dive below 600 feet, eventually
reaching an unprecedented depth of 3028 feet. How would it
have felt to be the first person to see the deep ocean? With
your instructor's approval, research the bathysphere and then
write your own short story based upon these dives. Color the
history with a fictional dialogue between yourself and the
support crew at the surface.
Spy
Stories
Learn
about "Project Jennifer" and the CIA's secret operation to
raise a Soviet sub from the seafloor. Using a modified research
vessel called the Glomar Explorer, the agency tried
to lift the hull into the secret compartment of this huge
ship. Check it out at http://www.fas.org/irp/program/collect/jennifer.htm.
WEB
CONNECTION
Marine
Operations at WHOI
Learn more about Alvin and the other research vessels at the
Woods Hole Oceanographic Institution.
Submarine
Construction
The basic construction of a submarine and its ballast tanks
are illustrated at this site.
William
Beebe - Going Deeper
Read this biography of William Beebe on The American Experience
Web site.
The
activities in this guide were contributed by Michael DiSpezio,
a Massachusetts-based science writer and author of "Critical
Thinking Puzzles" and "Awesome Experiments in Light & Sound"
(Sterling Publishing Co., NY).
Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools,
Wayland, MA
Suzanne Panico, Science Department, Fenway High School, Boston,
MA
Anne E. Jones, Science Department, Wayland Middle School,
Wayland, MA
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