>>9798429That's the correct answer, in a completely sealed jar the weight will begin at 1.5kg and slowly decay to a stable ~1kg, with the force being converted into heat and the air dynamics creating a swirl that dissipates the pressure equally to every side of the jar, including top and bottom.
Since you cannot have an experiment like this in a completely closed jar without the flies getting swept to the sides by the vortex, the closest we can have is this
https://www.youtube.com/watch?v=N0IGrSjcBZs which applies the weight as a force but as the system is open, cannot create a swirl to dissipate it sideways.
