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OBJECTIVES:
You will learn the basic types of pumps and how they
work in terms of pressure, velocity, and elevation differences.
You will build two examples of gravity-driven water pumps.
STEPS TO FOLLOW:
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Review the information in the background section.
We will use a pressure difference (sucking) to start the flow and
then explore the effects of elevation on the flow.
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Fill a large container with water
and place on the edge of a desk or table.
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Put one end of tubing in the container
and hold it over the other container on a chair
next to the desk or table. Raise and lower the
other end of the tubing over the second container.
Nothing will happen - there is no fluid in the
tubing and nothing to make the fluid flow.
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MATERIALS:
- Two large bowls or containers - not glass
- 2.5-3' of plastic tubing
- Tabler
- Chair
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Keep the one end of the tubing submerged
and gently suck at the tubing until water fills the
tube. Cap the end and quickly bring it down below
the level in the first container over the second
container. The water will flow into the second
container.
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You can see the different velocities
of the flow if you slowly raise and lower the
second end. The lower it is from the water level
in the first container, the faster it will flow.
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If you raise the end of the tubing above the
water level in the first container, the water will run
back down the tubing into the first container and
all flow will cease. You will have to reapply suction
to get the flow started again.
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Variation: As the water is
flowing from container 1 to container 2, put both
ends of the tubing under water and slowly lift
container 2 above container 1. The flow will
reverse itself and go from container 2 to container
1! To see this best, be sure to keep the tubing
filled with fluid.
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