This whole "deflategate" thing would be a wonderful high school science project. At 08:09 AM 1/27/2015, rcs@xmission.com wrote:
Won't there be condensation inside the ball? Is this normal? ----- Quoting Mike Speciner <ms@alum.mit.edu>:
A quick calculation of decrease in pressure caused by decrease in temperature... Assumptions: (1) volume unchanged [rigid container] (2) sealed container (3) initial pressure 12.5 psi at 24C, 100% humidity air (4) except for H2O component, assume ideal gas (5) final pressure calculated at 6C (6) pressures above are relative to atmospheric pressure, 14.7 psi
Calculation: partial pressure of H2O at 24C is .433 psi; partial pressure of remaining gas is thus 26.77 psi partial pressure of H2O at 6C is .135 psi; partial pressure of remaining gas is 279/297*26.77psi = 25.15psi Total pressure at 6C is then 25.15+.135 psi = 25.29 psi (10.6 psi relative to atmospheric pressure)
I’m dubious about the “rigid container” assumption. I think the ball is likely to exhibit elastic properties that are quite important. Why else is the pressure meaningful, other than that the ball can be deformed more or less when thrown or caught? Elasticity in the container walls would make it more like a constant pressure rather than a constant volume container. A good experiment would be to measure the pressure vs. volume curve for the ball. Perhaps our high school physics department can work on that.
On Jan 27, 2015, at 11:13 AM, Henry Baker <hbaker1@pipeline.com> wrote:
This whole "deflategate" thing would be a wonderful high school science project.
At 08:09 AM 1/27/2015, rcs@xmission.com wrote:
Won't there be condensation inside the ball? Is this normal? ----- Quoting Mike Speciner <ms@alum.mit.edu>:
A quick calculation of decrease in pressure caused by decrease in temperature... Assumptions: (1) volume unchanged [rigid container] (2) sealed container (3) initial pressure 12.5 psi at 24C, 100% humidity air (4) except for H2O component, assume ideal gas (5) final pressure calculated at 6C (6) pressures above are relative to atmospheric pressure, 14.7 psi
Calculation: partial pressure of H2O at 24C is .433 psi; partial pressure of remaining gas is thus 26.77 psi partial pressure of H2O at 6C is .135 psi; partial pressure of remaining gas is 279/297*26.77psi = 25.15psi Total pressure at 6C is then 25.15+.135 psi = 25.29 psi (10.6 psi relative to atmospheric pressure)
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