Slide 3 of 12
Notes:
If the fluid is incompressible, then the density is constant, and only the velocity of the fluid changes when the cross-sectional area of the pipes changes.
If you’ve ever squirted someone with a hose, you know that the speed of the water coming out of it increases when you turn the nozzle to make the opening smaller. If you don’t have a nozzle, you do the same thing by putting your thumb or finger over the opening. Of course, you are also reducing the flow rate when you do that by increasing the viscous resistance to flow, but the main reason the speed of the jet of water from the nozzle increases is the equation of continuity.
