A fire hose of internal diameter 7.5cm delivers water from ground level to a nozzle held 10m above the ground. The pressure in the hose at ground level is 3.0×105Pa (gauge), and the average speed of water in the hose is 2ms−1. The nozzle is required to eject a jet of water horizontally at a speed of 25ms−1.
(a) Calculate the diameter of the nozzle that will give the required jet speed.
(b) Determine the gauge pressure of water just inside the nozzle at the height of 10m.
(c) Explain why the pressure obtained in part (b) is lower than the pressure at the base of the hose, even though the water has been raised to a higher level.