An animation of <a href="https://en.wikipedia.org/wiki/Boyle%27s_Law" class="extiw" title="w:Boyle's Law">Boyle's Law</a>, showing the relationship between volume and pressure when gas mass and temperature are held constant.
NASA's Glenn Research Center
<a rel="nofollow" class="external free" href="http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html">http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html</a>