I have been involved in a fairly furious debate about a fluid dynamics experiment regarding the pressure of air passing through a tube attached to a moving car. It is similar in concept to the issue of whether or not an opening in an aeroplane fuselage would suck people out, where the opening did not interfere with the airflow. The situation is in the accompanying diagram. So the controversial issue is whether or not the pressure monitor would show a pressure which varies with the velocity of the car and whether the pressure it reads would be ambient pressure. This is more tricky problem than appears, and many many people who ought to get the answer right and are versed in physics seem to get it wrong initially. The issue to consider is whether Bernoulli's equation applies etc etc. I feel very strongly for one position but I thought I might ask for opinions on this first, hopefully which would confirm my position. I have a friend who is proposing to test this in the field with a car and some plastic tubing of about 2cm in diameter. If anyone can suggest potential problems with the test ( such as the difficulty of aligning and maintaining alignment of the T piece ) I would appreciate it.