Hi, I'm doing some research into the hydraulic jump and was wanting some help in calculating the impact force. The equation I have found to use is: F = m g h / s I have the mgh, and was wondering what to use as the slow down distance. If you didn't know what the hydraulic jump was, it is a phenomenon to do with the turbulence of the water - it is the 'ring' around the stream of water when a tap is turned on. I have been saying in my essay that the jump occurs when the water has slowed down enough. If that is my argument, then should I be using my values of the radius as the slow down distance? Also, how should I be demonstrating it on a graph? Two of my experiments I wanted to compare were the height above the surface (h) and the density of water I was using (m) to see which affected the radius more. g is really the only constant, and there is no set variable (because I'm comparing two of them to see which affects the radius the most) - so what advice would you have? Many many thanks, and I do apologise if this is a little incoherent; I'm quite tired and need to get this done soon :) Update: Maybe if F were the gradient, then that would be easily comparable, so mgh on x-axis, and s on the y??