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OBJECTIVES:
Studying air and water pressure with these activities
are fun ways to learn about basic fluid dynamics,
a key concept in Mechanical and Aeronautical and
Astronautical Engineering! In these efforts, students
will be able to demonstrate different ways to show
the effects of air and water pressure!
STEPS TO FOLLOW:
Lifting Objects With Air Pressure
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Activity 1:
Blow up a small round balloon.
Holding it over a student's mouth,
have him/her blow upwards in a steady stream.
The balloon will lift up and float above the
student's mouth! However since a balloon
is so light weight, this might not surprise the students.
In the next step the students use a heavier object.
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Using a student volunteer, ask him or her to blow upwards or
through a straw pointed upwards.
Place the ping pong ball in the airstream.
It too will lift up and float!
A ping pong ball is heavier than a balloon,
but it still rises. Both objects are round
the blowing air has to turn and travel
around the object. Since the air is moving over the sides,
the air pressure is lower on the sides,
and higher on the bottom of the object.
There is more air pressure on the bottom than the sides,
so it rises a little and appears to float in the air stream!
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Activity 2:
Do you think you can use air to lift a book?
Place a thick book on the table or desk.
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Place a balloon under the book and start to
blow up the balloon. As the air pressure
in the balloon increases (as it fills), the book
will start to rise up off the table! Depending
on the size of the book and the balloon, this
may work better by first blowing up the balloon,
then placing it under the book. The concept
is the same, but it's more dramatic using the first method!
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MATERIALS:
Balloons
Ping Pong Ball
Drinking Straw
A Thick Book
Deep Baking Pan (To Hold Water)
Aluminum Foil, Cut Into Squares (2 Squares Across The Width Of
A Sheet)
Pennies Or Small Washers
Large Spool Of Thread
1 Index Card
Small Margarine Or Yogurt Container, With Lid
Scissor Or Knife (To Cut Holes In The Container)
Masking Or Duct Tape
Holding Objects Up With Water Pressure
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Activity 3:
Using a square of aluminum foil fold
the foil to make a small boat. The boats
should be wide enough to hold the pennies
or washers. Fill the baking pan halfway with water.
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1-3 students can place their boats in the
water. Gently add the pennies or washers
to the boats, one at a time. Initially, the
boats will float with their load, but when too
many pennies are added the boats will sink.
Make a contest out of it! Whose boat can
hold the most pennies? Who has the best
design? What happens if you just wad up
the square of foil and put it in the water?
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Holding Objects Up In The Air
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Activity 4:
Place the index card
below a spool of thread.
Let go of the card. What happens?
(The card drops, of course.) Now blow into the
spool while holding the card, then let go of
the card while still blowing. The card stays put!
The air blowing out of the spool over the top
of the card causes a reduction in the pressure
at the top of the card. The pressure on the
underside of the card is higher, so the card
stays beneath the spool, rather than dropping.
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Activity 5:
Poke holes in both the bottom and the
lid of the margarine or yogurt tub.
Tape over both holes. Holding it over the
empty baking pan, carefully
pour water into the tub. Put on the lid.
Now pull away the tape on the lid. The water comes out in a stream.
When you pulled the tape from the bottom,
the air pressure on the outside of the tub
was greater than the pressure on the inside,
and greater than the weight of the water,
so the water didn't come out. After the
top piece of tape was pulled off, the air
pressure on the top and bottom of the
tub was equal, and the weight of the
water caused it to stream out of the tub!
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