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# Physics/Thermodynamics

Question
QUESTION: 1.Is it possible to have a process in which pressure is directly proportional to volume of the system????

2.Does pressure of balloon(considering as a system) increase while it is inflated??

ANSWER: Pressure is, in general, inversely proportional to the volume of a system and not proportional to it.  Usually there are small corrections, but that's the usual system.  I can't think of a system where the pressure would be proportional to the volume, no.

For a rubber balloon, the pressure as it is inflated is very complex.  At first, when the balloon is blown up and the rubber walls are thick, but the area inside the balloon is low, then no.  The pressure drops as you blow it up.  Just before a balloon breaks, the material should reach a stretching limit.  This would work better with something like a mylar balloon, which will stretch very little.  In a mylar balloon, the pressure would start low until the balloon started to have to stretch, then it would rise until the balloon pops.

---------- FOLLOW-UP ----------

QUESTION: Why does the pressure drops as i blow up a rubber balloon???Please explain.

Thanks...

The walls get thinner, and therefore weaker.  The surface area against which the pressure difference can push increases, increasing the force it can apply.  These factors dictate that when you first start blowing up a rubber balloon you must apply more pressure to get air in.  That fits with experience, and once the air starts to go in then it gets much easier to get more air inside.

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

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I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.