A horizontal jet of water of cross-sectional area A A\,A and density ρ \rho\,ρ strikes a vertical wall normally with a constant speed vvv. Upon striking the wall, the water loses all of its horizontal momentum and flows away parallel to the wall, as shown in the diagram.
Which of the following expressions correctly represents the magnitude of the force F F\,F exerted by the water on the wall?
F=ρAvF = \rho A vF=ρAv
F=12ρAv2F = \frac{1}{2} \rho A v^2F=21ρAv2
F=ρAv2F = \rho A v^2F=ρAv2
F=2ρAv2F = 2 \rho A v^2F=2ρAv2