Ok, so i've been getting confused about some things recently. I've read that fluid flowing in a pipe at higher velocity has less pressure than one flowing slowly. So this means that the less pressure the fluid has, the more momentum it has as it has greater velocity. So suppose I were trying to clean a surface with a high pressure washer, i know from experience that the water hits the ground harder than if i just used a hose by itself. Now, if i have a pump at high pressure, it means that it should have low velocity right? why is it then that high pressure pumps are better at cleaning surfaces than low pressure pumps if the water should have less impact. Also, if i had a water flowing from a bigger pipe to a smaller pipe, i would have a velocity increase by conservation of momentum and so get a pressure drop right? so does this mean that the water coming out of a small pipe, even though it has less pressure, would be better for cleaning than the larger higher pressure pipe?