# Why does the water appear to be in front of the pipe?

I recently visited an exhibition (at Questacon), where I saw a display that apparently exhibited the Coriolis effect.

There are four water jets coming out of pipes connected to a central spindle. Two pipes point out (NE and SW in the photo), and the other pair (NW and SE) are C-shaped, so the jets point in, towards the spindle. With the handle, I could rotate the spindle, which was solidly connected to the pipes.

Upon rotation, the outward-pointing jets acted as I would expect. The pipes were "in front" of the jets, with the jets themselves dragging behind (in terms of their angular position).

However, the inward-pointing jets were surprising to me. Instead of dragging behind the pipes, they instead appeared to push in front of the pipes.

I couldn't wrap my head around this. The explanation mentioned the Coriolis effect, but was unfortunately lacking in a more specific description. Why are the inward-pointing water jets "in front" of the pipes?

This happens due the initial tangential component of the jet velocity, which is also a cause of the Coriolis effect. It is depicted as vector $$v_t$$ on the diagram below and, as you can see, it deflects the jet from the radial direction.
A three step time sequence, depicted on the same diagram, shows that, at $$t_3$$, the jet, formed by three yellow dots, will be ahead of the pipe. The two leftmost yellow dots are shown as green dots at $$t_2$$. The leftmost yellow dot is shown as a blue dot at $$t_1$$.