Materials:
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- bendable soda straw
- round cheese ball (Cheetos or Planters snack product) for each
participant
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| Directions: |
- Special Directions:
- Reverse the straw, putting the non-bendable tip in your mouth.
Bend the straw upward, hold the cheese ball about 1" above the straw tip, and blow.
The cheese ball will remain suspended above the straw for as long as you can blow.
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| Safety Concerns: |
- Plenty of straws to go around and extra cheese balls for eating
will discourage students from using one another's straw or eating cheese balls that have
fallen on the floor.
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| Questions: |
- Can you "hold" a cheese ball in the air without touching
it?
- Where does the cheese ball "ride"? Why?
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| Concepts: |
- This activity involves several scientific concepts. For starters, redirection
of the moving air through the straw results in upward momentum according
to newton's 3rd law. Next, Bernoulli's Principle is involved, in keeping
the ball from drifting off to one side and dropping out of the air stream.
Recall Bernoulli: faster moving fluid is at a lower pressure than slower moving
fluid (all other factors being equal -- this is a bit simplified). So the fast
moving vertical air stream from the straw (flowing past the Cheeto) is at a
lower pressure than the surrounding, relatively stationary air. The high pressure
surrounding air pushes all items towards the center of the stream, keeping
the Cheeto from drifting to any one side.
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