I've done first year warwick maths, and chose the physics classical mechanics (and special relativity, but I don't think that'll help here
) module as an option. So far as I remember they weren't mentioned
I got a good first in the module, but then it was more mathsy than physicsy, I suppose.
I've always been taught that gravity is a strictly attractive force - at least in the 3 physics modules we did it was taught as one.
Hmm. I'm afraid I haven't a clue what a pressure differential is (although I could make a guess)- I would guess you're meaning a substance which has the same pressure as the helium in the balloon, but has a greater mass/weight?
I'm not sure what would happen in that situation. I'm trying to decide whether its even possible to have such a surrounding material? I'm sketchy on the gas laws, but I would have thought that pressure is proportional to density - so you wouldn't be able to have a fluid with greater density without it having a higher pressure than the helium (?)
So, at least how I would explain it under a purely attractive gravitational force, the helium balloon would rise because of the pressure of this new fluid being greater than the pressure of the balloon. Maybe.
Though then I realise that that maybe doesn't give a reason for why the balloon should rise - the fluid could push it down?
I'm going to assume that something to do with gases/stuff means that lower pressure always feels a force upwards (when surrounded by higher pressure)
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