A bubble in a vaccum has a radius 7cm and another soap bubble in the vaccum has a radius of 10cm.if d two bubbles comes together under isothermal condition.calculate the radius of the bubble formed

Question

souvik · Answer

here temperature is fixed..and so the volume.
using Boyle's law..
$$P _{i}V=p _{1}V _{1}=p _{2}V _{2}$$
or  $$P _{i}V=p _{1}V _{1}+p _{2}V _{2}$$
where $P _{i}$ is the internal pressure of the new bubble
$p _{1}$ & $p _{2}$ =the internal pressure of the two bubble respectively
V is the volume of the new bubble
$V _{1}$ & $V _{2}$ = their volume respectively
now u can find $P _{i}$
and the radius of the new bubble

anonymous · Answer

But since its vacuum, how can it have an internal pressure?

souvik · Answer

the pressure outside the bubble is zero...right?

anonymous · Answer

yes.. but the pressure inside should be higher right? .. but if its vacuum , how can that be possible? (what is stopping the bubble from shrinking due to surface tension)

souvik · Answer

the internal pressure is pushing the soap surface outside witch is balanced by surface tension..

anonymous · Answer

but what is creating that internal pressure?? :P.. there is no air.. right??

souvik · Answer

there must be some air..inside the bubble..if it is not..how could one make bubble..

anonymous · Answer

hmmm point ^^.. you put that air when you blow the bubble.. now why didn't i think of that :P

souvik · Answer

yes..:)

anonymous · Answer

can you please tell me what exactly is happening in this process...i want some explaination that can prove its recent mathematical approach