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Name: Al H.
Status: Other
Age: 60s
Location: N/A
Country: N/A
Date: February 2003

In the business I work in we had a discussion concerning precise measuring blocks called "gage blocks". These are stacked up to determine very close tolerances by rubbing (wringing) them together to remove the air between the two surfaces. If a stack of gage blocks were put into a vacuum, would the molecular attraction still hold them together or would they fall apart since air pressure is the same on all sides?

I do not quite understand what you are asking. The blocks are not held together by the film of air between the blocks. However, it is difficult to pull them apart rapidly, because doing so creates a vacuum between the blocks until air can rush in from the edges of the gap. More precisely, pulling the blocks apart involves pushing the atmosphere aside, which requires substantial force (air pressure times surface area). If the blocks were in a vacuum, they would not be so difficult to separate. Is that what you are asking?

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois

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