I recently asked for help in planning some demonstrations and hands-on
learning activities on the wonders of Bernoulli for a group of 5th grade
scouts. Below is a summary of the ideas offered from almost two-dozen
respondents. Thanks to all.
Dave
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1
Get an inflated beachball and throw it with a strong spin. The path curves
substantially according to the Bernoulli prediction. Or us ping pong or
styrofoam ball.
2
Get a thin-spout funnel and a ping pong ball. Invert the funnel (spout up)
and blow down through it. Place the pp ball up into the funnel as far as it
will go while blowing. Let go of the ball while continuing to blow. The ball
(seemingly) miraculously stays snuggly up into the funnel as the air stream
blows down around the ball. The narrow neck is needed so a complete lung full
of air will last for a few seconds. If the funnel is made of clear glass or
plastic the students can easily see the ball suspended inside the funnel
through the side of the funnel. (After you run out of breath the ball falls
down showing that you did not cheat by sticking the ball to the funnel with
some sticky foreign substance.)
3
Get a thin rectangular piece of paper and place one end of it tightly
against your lower lip while letting the rest of the paper strip protrude out
from and down from your lip. Blow over the paper. It rises up toward the
main airstream. It is best to have a short (1 cm) section of the paper up
against your lip with a flexible crease in the paper 1 cm from the lip end.
The crease provides a loose pivot for the rest of the paper to rotate about.
(It also prevents cheating by stiffening the paper by holding it with a slight
longitudinal curl allowing the paper to stick straight out from your face
whether or not you are blowing.)
4
....our book mentioned the shower curtain being drawn into the shower...
5
What you do is blow up a balloon, you want it as spherical as possible.
Point the end of the (reversed) vacuum nozzle up, hold the balloon over the
nozzle, and increase the voltage (optional Variac) to the vacuum. If you do it
right (It takes some practice) you should be able to suspend the balloon in a
jet of air about 2m above the end of the nozzle. You now tilt the nozzle (max
of about 30 degrees from verticle) and the balloon moves staying in the air
stream. If you go to far it will fall out. This can also be done with a
ping-pong ball.
6
How about a pivoting wing that "flys." This can be done with a
counterweighted lever-arm and axle riding in a yoke:
wing ___ ____
-----_________________________| o |___/ |weight
|_____-------------------------| |---\____|
| |
______| |_______
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FRONT VIEW
(I haven't tried any of this, I'm just speculating here.)
A paper-and-tape "wing" goes on the far end of the arm. A blow-dryer or a
big fan on a desk provides moving air. Gobs of plasticine clay can be
used to adjust the weight.
I'm anti-Bernoulli, and the above activity is sort of subversive because
kids will quickly learn that large attack-angles give large lift...and large
drag.
7
Try a paper airplane contest and discuss the shape of wings.
8
Put a straw in water or some other beverage. Hold
the straw while in the beverage and blow a stream of air perpendicular to
the direction of the straw. The liquid should rise in the straw due to
less pressure in the straw...may even rise completely out causing a spray.
9
How about hanging two empty pop cans from their rings, side by side,
about 2 inches apart and then blow between them?
10
Get some spools with or without thread on them. They must have
flat ends. Stick a straight pin through the middle of a 3x5 card and
then put the card on the end of the spool so the pin goes in the hole
in the middle of the spool.
Then blow on the other end and you can't get the card to fall off the
spool. Even may be possible to turn the spool upside down.
11 Egg under a narrow water stream, as the water falls into a glass which
has a diameter slightly larger than the egg dimension. The egg will rise
out of the glass by about 40% of its height if everything is right.
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Good luck to me and to you all with Bernoulli.
Dave
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* David Simmons <dsimmon@uoft02.utoledo.edu *
* St. John's Jesuit High School *