Choked flow

Okay, kiddo! Do you know what happens when you try to drink water through a really skinny straw? It becomes really hard to suck the water out, right? That's because the straw is so narrow (like when you squish the tip of a balloon) that it won't let enough water through.

The same thing happens with gases- they can only flow through a certain size hole or opening, and if that opening gets too small, the gas can't flow anymore. This is what we call "choked flow."

Imagine a balloon full of air. As you let the air out, it comes out easily at first, but the more air you let out (and the smaller the opening gets), the harder it is to get the air out. Eventually, you might not be able to let any more air out at all because the opening is too small!

That's what happens with choked flow- when the opening through which a gas is trying to flow gets so small that it can't pass through anymore. This can happen in all kinds of situations- like when gas is flowing through a pipe and the pipe gets too narrow. When this happens, the gas can "choke" and stop flowing altogether!