12-28-2021, 04:23 AM
(12-27-2021, 12:13 PM)solid Wrote: To explain why only a 2 hPa peak (or peaks) are obtained out of about 35 hPa pressure in the balloon is really a question.
First of all I have verified pressure in the balloon blowing up. The technique using the SensorTag and a small jar which is cited above was applied. It gave also the maximum pressure of about 50 hPa (the pressure were reducing with the balloon growing, see figure).
Then the experiment of Eric was repeated with the black balloon. The material used is on the photo below. The needle was initially inserted in the wine bottle cork to pop the balloon inside the bag (and not trough it in order to preserve its hermeticity ).
The pop sound is so strong that the measurements by the SensorTag were stopped. The phone measured some peaks of about 2 hPa as is presented by Eric.
No explanation for the moment...
I popped 4 balloons with about 2 seconds interval but without any bag to see if I could get a pressure peak at all "out of thin air". I got two minor minima (not peaks!) that is probably from the last two balloons popping: 1007.53 and 1007.51 when average pressure was 1007.70 hPa (I should have measured when the pops happened with the Acoustic Stopwatch but I haven't mastered programming phyphox experiments yet).
So the immediate release of about 4.5 liters of 35 hPa air (without anything but air containing the release) somehow registers a decrease in air pressure.
Apparently, after an explosion, you can have a "negative pressure zone" and a "subsequent oscillation zone":
https://doi.org/10.1016/j.dt.2019.04.014
Not sure we're measuring any of that stuff, but in theory we might be doing exactly that!
Best regards.
//Erik