Calculating Friction Force, Mass and Gauge Pressure in an Emergency Tank

[jenha14]

A village maintains a large tank with an open top, containing water for emergencies. The water can drain from the tank through a hose of diameter 6.15 cm. The hose ends with a nozzle of diameter 2.35 cm. A rubber stopper is inserted into the nozzle. The water level in the tank is kept 7.50 m above the nozzle.
(a) Calculate the friction force exerted by the nozzle on the stopper.
(b) The stopper is removed. What mass of water flows from the nozzle in 2.00 h?
(c) Calculate the gauge pressure of the flowing water in the hose just behind the nozzle.


Do I need to use Bernoulli's eqution?

 

[Astronuc]

If friction holds the stopper in the nozzle, then the friction force must equal the force of the water, i.e. the pressure head.

Yes, use Bernoulli's equation.

The gauge pressure is just the absolute pressure minus the atmospheric pressure.