What makes a fluid flow?
There are basically two ways to make fluid flow through a pipe.
- Tilt the pipe and let gravity pull the fluid downhill.
- Make the pressure higher at one end of the pipe than the other. A pressure difference is equivalent to a net force, accelerating the fluid toward lower-pressure regions.
In our tube of varying cross-section, where is the pressure greatest?
- At the ends, where the tube is wide
- In the middle, where the tube is narrow