These are the problems I have to choose between for a school project entering a competition. There are other problems but these are the ones I'm torn between. Hydraulic jump When a smooth column of water hits a horizontal plane, it flows out radially. At some radius, its height suddenly rises. Investigate the nature of the phenomenon. What happens if a liquid more viscous than water is used? Ball spin Spin can be used to alter the flight path of balls in sport. Investigate the motion of a spinning ball, for example a table-tennis or tennis ball, in order to determine the effect of the relevant parameters. I would like suggestions on which of these might be more interesting, which would be easier to make something impressive out of, which is more experimentable (I'm definately leaning towards the hydraulic flow just because of this reason) and which should have the most available information. Just googling a bit I've found the following. For Ball Spin: http://www.google.se/search?q=cache:Vf2xE018DvQJ:physicsweb.org/article/world/11/6/8+football+spin+physics&hl=sv [Broken] For Hydraulic Jumps: (amongst many others) http://www.google.se/search?q=cache:tjqh5TfoikoJ:suuri.sci.ibaraki.ac.jp/~shinya/res/hyd.html+hydraulic+jumps+physics+polygonal&hl=sv [Broken] http://arxiv.org/PS_cache/physics/pdf/0208/0208079.pdf [Broken] http://info.fysik.dtu.dk/%7Etbohr/papers/Nonlinearitycover.pdf [Broken] I'm also wondering whether the polygonal status of the jump will be relevant to the project based on the definition of the problem and what is needed to cause the effect. I know this could/should be done by myself, but I have to decide now or early tomorrow, dunno why but my teachers are hogging me so what advice/comments can you provide regarding my decision on which to chose?