This is a simple question that I should've known, but I'll ask. Fluid jet with density $ flows with velocity V1 before it strikes a block, then goes in two perpendicular directions, like left, right with the same velocity V2 in opposite directions. Find the force on the block. My try: The decrease in kinetic energy density is converted into excess pressure energy, so it should be, but I'm a silly unsure person. Initial energy/vol = $V1*V1/2, Final energy= twice $ V2*V2/2 since there are two final flows. So the difference multiplied area of impact, force. $(V*V1/2 - V2*V2)*area = force. But the correct answer, they say, is $(V1*V1 -V2*V2)* area.