# How does Boyle's law affect hot air balloons?

Jun 25, 2018

Well, what does $\text{Boyle's Law}$ say.....?
It says that $P \propto \frac{1}{V}$...and thus it has NO FORMAL application to hot air ballooning...because pressure is formally constant. (Of course, as the balloon ascends, the atmospheric pressure DOES decrease...but to a first approx. we ignore this...)
On the other hand, $\text{Charles' Law}$ holds that $V \propto T$...and so if we enclose a volume of gas in a canopy, and give it a good blast with a gas burner the canopy inflates with hot gas...and will occupy a volume of air that MAY HAVE a greater mass than the mass of the balloon, the canopy, and the balloonists..and so the balloon floats...