Imagine a large diameter piston filled with water connected to a small funnel. When you press on the piston slowly but with considerable force the water will move very quickly from the funnel in form of a jet. But how is it possible on a molecular level?
Water molecules are constantly moving about in the piston with various speeds and directions bumping into each other and exchanging momentum like billiard balls, however water molecules from the funnel are moving uniformly at great speed.
I want to know how it is possible for slow molecules to be adding momentum to the ones that are already moving faster than the average. In billiard ball analogy slow moving ball moving in the same direction would never catch up with the faster one to further increase its momentum and if it was moving in the opposite direction then it could only receive momentum from the faster one and therefore only slow it down.
Now I imagine that this question probably sounds silly but I can't find any answer after searching for it, so I decided to ask here.