Which way do two hanging cans move when pressure in their gap becomes lower than outside?
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After you watchWhich way do two hanging cans move when pressure in their gap becomes lower than outside?
The short answer
When gap pressure is lower than outside pressure, the larger outside force pushes each can inward. The net force comes from a pressure difference.
Try this next
- What happens when the pressures balance again? Move the gap-pressure control back to zero after the inward motion. Compare the two opposing pushes.
- Does changing both pushes always move the block? Return to the practice block and increase both pressures together. Compare that result with changing only the can gap.
Now you — bend it
- What if What if you replay exactly the same starting conditions?Set the gap-pressure change to maximum and observe. Return it to zero to restore balanced pressure, then repeat.
Can you prove it?A matched comparison can test your prediction. — Set the gap-pressure change to maximum and observe. Return it to zero to restore balanced pressure, then repeat.
Design your own test:Choose a supported setting and predict its result before running it.
Explain it to a 6-year-old: When gap pressure is lower than outside pressure, the larger outside force pushes each can inward. The net force comes from a pressure difference.
The whole story
How it works
Air pressure acts on each surface. Equal opposing pressures balance in the practice block. The unseen can arrangement has outer and inner surfaces. Reducing only the gap pressure changes the net force, and the cans move inward against their suspension. The final explanation waits for the completed pressure change.
What people get wrong
The control sets an idealized pressure reduction; it does not calculate pressure from breath speed. Bernoulli’s equation has flow assumptions, and fast air is not always at lower pressure. Real jets and can geometry need their own flow analysis.
The catch
The control sets an idealized pressure reduction; it does not calculate pressure from breath speed. Bernoulli’s equation has flow assumptions, and fast air is not always at lower pressure. Real jets and can geometry need their own flow analysis.
Questions kids ask
Which way do two hanging cans move when pressure in their gap becomes lower than outside?
When gap pressure is lower than outside pressure, the larger outside force pushes each can inward. The net force comes from a pressure difference.
What can I change in this experiment?
Equal practice pressure, then gap-pressure reduction and reversible replay.
Does this model describe every real case?
The control sets an idealized pressure reduction; it does not calculate pressure from breath speed. Bernoulli’s equation has flow assumptions, and fast air is not always at lower pressure. Real jets and can geometry need their own flow analysis.
Talk about it
- If gap pressure becomes lower than outside pressure, do the hanging cans move apart or together?
- Which observation supports your explanation?
- What does this model leave out?
For grown-ups
Air pressure acts on each surface. Equal opposing pressures balance in the practice block. The unseen can arrangement has outer and inner surfaces. Reducing only the gap pressure changes the net force, and the cans move inward against their suspension. The final explanation waits for the completed pressure change. The control sets an idealized pressure reduction; it does not calculate pressure from breath speed. Bernoulli’s equation has flow assumptions, and fast air is not always at lower pressure. Real jets and can geometry need their own flow analysis.
Keep going
What else makes you wonder?
- What would you change for a new test?
- Which two things must stay the same for a fair comparison?
