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Fellows on a Bellows (Posted on 2007-02-28) Difficulty: 3 of 5
A platform is placed on top of an air-filled bellows that is about the size of a bathroom scale (say, 1ft x 1ft x a few inches tall). A small (~1in) tube connects to the bellows at one side, and rises up vertically. The other end of the tube is open to the atmosphere. A man of average height and weight arrives. He notices that the open end of the tube is about at eye level. The man steps onto the platform and the bellows completely collapses since the air from inside is expelled through the tube, which is the only path for it to escape. After the man steps off the platform the bellows refills with air, by virtue of the tube.

The bellows is then filled with water (all air is removed). The man again steps onto the platform. How much water is expelled from the bellows?

The man’s identical twin comes along and joins his brother on the platform. How much more water is expelled?

  Submitted by Kenny M    
Rating: 4.0000 (1 votes)
Solution: (Hide)
None, in either case. Assuming the man to be about 165 lbs., the bellows will support his weight without any water being expelled. In fact, the height of the water in the tube will only be about 2.5 ft above the top of the platform & bellows. This occurs because the height of the water column in the tube causes increased pressure as you go down the tube. The relatively large area of the bellows (1 sqft) multiplied by this pressure will then support the man. When both men are on the platform, the water column is merely twice as high as with either one.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionSolutionhoodat2007-03-01 14:21:35
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