Problem is simplied. Assume ideal gas @ atm pressure & temperature. Completely seal the needle end of a syringe. Assume bottom end of syringe is completely sealed (can move in axial direction). Q1. If I press on the syringe (pressurize inside), is if correct to say that the pressure increase on the inside of the syringe is equal to the pressure decrease on the outside (open to atm)? Q2. If non-sealed side of syringe is connected to a piping system in which a non-compressible fluid is flowing, a pressure increase in the fluid will cause a pressure increase inside the syringe. In this case is it correct to say that the pressure increase on the inside of the syringe is equal to the pressure drop in the fluid (piping system)?