I understand PSI is pounds of force per square inch. So through a nozzle if the pressure is higher, the water or whatever liquid going through will go further?
If water is flowing through a pipe at 100 psi that means per square inch of cross sectional area 100 pounds of force is being applied? So how would pressure be measured, I know the pressure=force/area but in a pipe would it be any different because there is volume of water? How would you measure force applied on the water by a pipe?

So if there was a 2 inch by 2 inch square pipe which had a pressure of 100 psi, the force would be 400 pounds on the water?