November Cub Scout Roundtable Issue

Volume 7, Issue 3

Turn Up The Power (Webelos Craftsman & Scientist)

 

WEBELOS

Scientist

Bernoulli's Principle

Bernoulli's Principle And How Wings Work

Daniel Bernoulli was a Swiss scientist born in 1700. He discovered that fast moving air exerts less pressure than slow moving air. This same principle makes airplanes and gliders fly.

Experiments:

  1. Paper Strip Experiment
    Cut a piece of paper 2" by 6". Hold the narrow end, with the other end hanging down, in front of your mouth and blow across the top. Most people think the paper should go down as you blow across the top but surprisingly the paper rises up. This is because the air you blow is moving faster than the air under the paper. That means there is more pressure on the underside than the top.
  2. Ping-Pong Balls Experiment
    You need: 2 Ping-Pong balls, two 12" pieces of string, tape, and a ruler. Tape one end of the string to the Ping-Pong ball and do the same on the second one. Tape the other ends of the strings to the ruler so that the Ping-Pong balls are hanging about 1" apart. Hold the ruler up so that the balls hang freely. Now, blow between the balls from a distance of about 3". The balls should pull toward each other. This is because the air traveling over the curved surfaces of the balls is faster and therefore has less pressure than the air on the outside of the balls.
  3. Paper Wing Experiment
    Cut a 4" by a 8 1/2" piece of paper and fold it in half. Tape the narrow edge one inch from opposite edge so that a wing with a flat bottom and curved top is formed. Slip a ruler through the wing loop end opposite the taped end with the curved side up. Now, blow directly at the folded part. The wing should rise up. This shows how Bernoulli's principle applies to wings and flight.
  4. The Ball and Funnel Challenge
  5. Materials: Ping-Pong balls, a few large funnels
  6. Experiment: Let the scouts know that it is time to have a little contest--you are going to see who can blow a Ping-Pong ball out of a funnel the easiest. All you must do is give a ball and funnel to each participating scout, have them place the ball in the funnel, and then try to blow the ball out as far as they can. The ball won't move! In order to blow the Ping-Pong ball out of the funnel, you must blow across the top of the funnel. This activity can also be done by hooking a blower hose to the end of the funnel in order to provide a constant blowing air supply. The funnel can then be held upside down, swung around, etc., and the ball still will not fly out!
  7. Water Up a Straw
  8. Materials: a tall glass of water, drinking straws
  9. Place one straw into the glass of water, holding it upright and keeping the bottom of the straw just off the bottom of the glass. Next, blow a short, hard blast of air through the second straw, holding it so that it is perpendicular to the first straw and their ends are touching. Water will come spraying out of the first straw into the air.
  10. By blowing over the top of the first straw you decrease the pressure in that area (due to the increased air velocity). This causes the water to be pushed out of the top of the straw by the higher pressure at its base.

 

Egg in the Bottle

Peel a hard-boiled eggs just before doing the demonstration. .Set a small piece of paper on fire and drop it into the bottle. Place the hard-boiled egg on top or the opening of the bottle, small end first. The egg will be pulled into the bottle after the heated air from the fire has contracted. (As the air was heated, it began to expand. When the fire was extinguished, the air began to cool and contract. The egg seals the bottle. There is less air in the bottle causing unequal pressure to occur between the air in the bottle and the air outside the bottle. The air pressure on the outside pushes the egg into the bottle equalizing the air pressure inside and outside the bottle. Air pushes on all surfaces that it touches. This push is called air pressure.

 

Science Revelations

Webelos dress as mad scientists (lab coats, wild hair). They can come out and state these "facts" as written by students. Be sure to let your audience know that this is strictly humor, that comes from test papers and essays submitted to science and health teachers by elementary, junior high, high school, and college students and compiled at the NEA Life Sciences Symposium, Kansas City, Kansas.

  1. "The body consists of three parts - the branium, the borax, and the abominable cavity. The branium contains the brain, the borax contains the heart and lungs, and the abominable cavity contains the bowels, of which there are five - a, e, i, o, and u."
  2. "H2O is hot water, and CO2 is cold water."
  3. "To collect fumes of sulphur, hold a deacon over a flame in a test tube."
  4. "Three kinds of blood vessels are arteries, vanes and caterpillars."
  5. "Blood flows down one leg and up the other."
  6. "Respiration is composed of two acts, first inspiration, and then expectoration."
  7. "Dew is formed on leaves when the sun shines down on them and makes them perspire."
  8. "Mushrooms always grow in damp places and so they look like umbrellas."
  9. "The pistol of a flower is its only protections against insects."
  10. "A fossil is an extinct animal. The older it is, the more extinct it is."
  11. "Germinate: To become a naturalized German."
  12. "Liter: A nest of young puppies."
  13. "Momentum: What you give a person when they are going away."
  14. "Rhubarb: A kind of celery gone bloodshot."
  15. "To keep milk from turning sour: Keep it in the cow."

 

 

Materials found in Baloo's Bugle may be used by Scouters for Scouting activities provided that Baloo's Bugle and the original contributors are cited as the source of the material.




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