Up: Glassmaking
Gilbert: 26 of 65
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Experiment 19. To make a submarine.
Close one end of a piece of No. 2 tubing
as described above, but leave the end somewhat pointed (1,
Fig. 32). Heat the tube on one side at a distance
½ inch from the end and blow a bulb about ½ inch in
diameter (2). Heat the tube ¼ inch from the bulb, draw it down
into a fine tube, and break off the tube, leaving a small hole in the
end (3). Place the submarine in a glass of water, and if it floats it
is complete.
FIG. 33
THE SUBMARINE
SUBMERGES
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Experiment 20. Magic.
Fill a bottle to overflowing with water,
insert the submarine open end down, insert the solid rubber stopper
and press down hard (Fig. 33). Does the submarine submerge?
Release the stopper. Does the submarine
rise and does it also move forward?
Turn the bottle on its side and release
the stopper quickly. Does the submarine shoot forward at a great
rate (Fig. 34)?
The submarine acts in this magical manner
for the reasons given in Experiment 9. When you press
the stopper in, you compress the air in the submarine and force water
in until the submarine weighs more than an equal volume of water and
it sinks. When you release the pressure on the stopper, the compressed
air forces the water out until the submarine becomes lighter than an
equal volume of water and it rises. The water rushing out through the
opening exerts pressure backwards in the water in the bottle and the
reaction drives the submarine forward.
Experiment 21. Fun with the submarine.
If your friends do not know about the
little submarine, you can mystify them as follows: Tell them that
submarines are
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