# Pressure and energy ?

1. Apr 24, 2012

### Hypo

Hallo everyone!

Im new here on this forum and I had a few questions in mind I would like to share them with everyone to get a perfect understanding with what I'm dealing with.

Now what is Pressure exactly? Is it a force or energy? Im kinda confused about it...?

For example the pressure from a compressed air tank blowing out through a small spot is that energy or force coming out?

Another example a ballon having a very very small poked whole to it... The air coming out from the pressure is that energy or force?

Thank you everyone :)

2. Apr 24, 2012

### Drakkith

Staff Emeritus
Energy is the ability for one system to perform work on another system. A compressed gas or a balloon has the ability to perform work on the gas outside by releasing it's own compressed gas. The gas has lots of kinetic energy as it exits the tank/balloon thanks to pressure generated by the compression inside the tank, or the squeezing by the balloon. So to answer your question, it is neither energy nor force coming out of the tank or balloon, it is gas molecules that are in motion which have energy and exert a force on other molecules.

The definition of pressure itself is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.

3. Apr 24, 2012

### haruspex

Consider a second balloon, twice the size of the first, same pressure. It has twice the potential to do work (energy), but the same pressure, so they're different things.

Consider a vessel of compressed gas with a bung in the top. A wide bung would be hard to keep in because its area is larger. Force = pressure times area.

4. Apr 24, 2012