Ed that's the definition of vacuum. Negative pressure. I don't think it's like temperature, where absolute zero is defined by the point at which air molecules are no longer moving, and 0 C and 0 F are just human-dictated baselines. The baseline of pressure/vacuum is kind of the same way, as 0 is dictated by ambient conditions/14.7 psi/conditions at sea level at STP.Quote:
Originally Posted by DRAGOONRANCH
so here's another way of thinking about the original question: If you take the spark plug out of cylinder #1 at TDC, put a wrench on the crank and turn it a quarter turn, would you say "aw dang that there feels like a lack of atmospheric pressure," or would you say "that feels like vacuum?" Also, does a carb work just the same with atmospheric pressure on all sides (ie without a vacuum behind it) as it does with the vacuum on the manifold?
I understand that in an academic, "frictionless surface" type environment this question is probably fine. The cylinder appears out of nowhere and has no pressure in it. Atmospheric pressure might fill the cylinder. However, this test specifies at the beginning that it was designed to test the ability of tractor mechanics to learn/understand stuff. Vacuum created by increased volume in the cylinder definitely achieves that end better than "atmospheric pressure"
and for you douchebags who want to pick at my formula, it was Boyles' law, not the universal gas law, because n and r are constant in this case. John you should know that since you fancy yourself a diver.
