Question about a fountain 
There's this fountain where I work. I haven't really studied fluid dynamics, so my question is about how it works. 
The way the fountain is designed, is that there is one long big pipe that runs down the middle of the fountain. There are holes drilled into the pipe about every 8 inches or so. Into this holes goes a little clear plastic piece of pipe making a jet for the water to go straight up.
My question is: how are all the "jets" pushing water to about the same height? Intuition would tell me that the water would be higher at one end or the other..the end that the Lon main pipe is connected to the pump. I would assume the water height of the jets to taper off the further away from the pump.
I hope that makes sense.
Thanks,
Kyle
 A: There would be a slight difference in height, but obviously they design these to be negligible.
The key issue is the drag on the water from the inside surface of the pipe.  If you were to explore this system in a static situation (no water movement), you would find the pressure at the outlets of each fountain was exactly the same.  However, as we have water movement, we see drag.  This drag will decrease the pressure the final fountain outlet sees.
One solution to this is to use a large enough pipe to simply ignore this effect entirely.  Another is to counteract the effect by making the pipe more narrow as you go to convert some of the water's dynamic pressure due to velocity into static pressure (which is what you need to spray out of the outlet).
This effect can be observed in several places.  One is a children's toy for the pool, which shoots a large stream of water using this effect.

And another place you can see it is in air conditioning vents.  Next time you are in a large commercial building where the air conditioning vents are exposed, take a good look at them.  The vents are very large near the air conditioner itself, and at every outlet (or nearly every outlet), they decrease the diameter of the venting.  This keeps the output of each vent equal.  You can see the vent go from right to left in this picture.

A: As @Cort Ammon alluded to, one aspect of designing this is to make the pressure drop through each jet large compared to the pressure variations along the large pipe.  This will guarantee that flows through the jets are uniform.  Another contributor to this is the Bernoulli equation which tells us that, in the absence of viscous frictional drag, the pressure would actually increase toward the dead end of the header pipe (since the flow is decelerating axially).  In designing the real system, both the viscous frictional drag and the fluid inertia should be taken into consideration.  It would also be possible to taper the pipe contour to minimize pressure variations along the pipe, but this would probably not be cost effective.  Another possibility would be to vary the jet lengths and diameters along the length of the main pipe.
