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Guide to Propulsion
- Before you
begin: Observation of pop can at room temperature.
Students may measure the can and note
that it is a normal "empty" pop can.
- Observation of
pop can with boiling water.
Students should note the moisture leaving
the can and that its size and shape remain unchanged.
Also, the air inside the can has increased in temperature.
- Observation of
pop can after inverting it in ice water.
The can implodes very quickly.
Students' descriptions will vary but stress for detail.
Allow discussion within the lab group.
diagrams of the pop can as it appeared: at room temp , with boiling
water, immersed in ice water.
At room temperature and with boiling water
the force arrows are in balance.
When immersed in ice water the atmospheric air pressure is much larger
than the air pressure inside the can.
- Explain how air
pressure changed the pop can during the procedure.
Both the can at room temperature and the
can with boiling water were at equilibrium, forces in balance. Although
the can with the boiling water had fewer gas molecules per unit volume,
it did not implode because those heated molecules were moving much
faster and equalizing the force of atmospheric pressure. Once the
can was put in the cold water, the heated gas molecules lost kinetic
energy to the ice water and slowed down. Now unable to equal the force
of atmospheric pressure the can implodes. NOTE: Many students will
say that the can was "sucked in." Use this as an opportunity to inform
them that "Science doesn't suck!" You may even make them write that
Is the can empty?
No, it contains gas molecules (mostly
nitrogen and oxygen and water vapor).
A. What happens to air pressure as air travels through the engine
from 0 to 8?
is an overall increase in air pressure.
How does molecular motion change from stations 0 to 8?
There is an overall increase in molecular
C. What is one function of a gas turbine engine?
To increase air pressure, molecular motion,
- After studying
air pressure and gas turbine engines, list three questions that you
and your lab partners now have about this topic.
Answers will vary.
The instructor may use this as a springboard to an extension to this
lesson. The instructor may opt to explore topic(s) as a class or to
divide the class into small groups that will report their findings
to the class.
A good place to start is the Beginner's
Guide to Propulsion.
Propulsion Activity Index