1. The problem statement, all variables and given/known data Water flows at a speed of 0.75 m / s through a U-shaped tube whose cross-section is circular with a radius of 10 mm. How large is the force F to be to compensate for water power on the tube? 2. Relevant equations I am not sure. Perhaps; Pressure=Force/Area Conservation of momentum Density = mass/volume 3. The attempt at a solution I believe that the speed of water flow is the same through the whole pipe but the velocities have different signs in each side of the pipe. Of course the mass is constant.if I use conservation of momentum I will have: Fdt=m(Δv)=m(v_1-v_2)=m(v-(-v))=2mv Fdt=2mv. The mass is not given but if we knew the volume we could find it as m=ρV. And how can I separate F from Fdt? I tried this(wrong); Fdt=2mv=2m(dx/dt) --->F=2m(d^2x/dt^2)=2ma=0 since velocity is constant.