On: Feynman Sprinkler [video]

[snewman]

My understanding here is shallow, but I think you are correct.

Here's a simple exercise to help your intuition: open your hand up flat, and hold it facing your mouth, a few inches away. Blow, and you can easily feel the air pressing on your palm. Now inhale sharply; your hand will feel no suction at all.

[jojobas → snewman]

That's true, but all the air molecules entering a tube aligned with X axis have negative momentum along X. You'd think this means the total X momentum of all molecules become more positive.