Hello students (and also others) at iMechanica,

Last weekend, while channel browsing on TV, I happened to notice a documentary on the Hoover dam (in the US). It showed a number of jets of water, huge ones, forcefully springing forth out of the rock faces just downstream of the dam. These were the water jets coming off the electricity generation plant of the dam, *after* their job of generating electricity was already over.

Watching these fascinating water streams reminded me of a brain teaser. Might as well share it here. (It might look like high-school physics, but you can use it to understand higher courses in engineering as well.)