The water supply of a 36-story building is fed through a main 8-centimeter diameter pipe. a 1.6-centimeter diameter faucet tap located 22 meters above the main pipe is observed to fill a 30-liter container in 20 seconds. what is the speed at which the water leaves the faucet?

1 Answer
Jun 22, 2014

Assuming the water leaves the facet with a speed V m/secVmsec, the amount of water that goes through this facet in 1 sec1sec equals to the volume of a cylinder of a height V mVm and a diameter of a base 1.6 cm1.6cm (radius 0.8 cm = 0.008 m0.8cm=0.008m). So, in cubic meters it's equal to: pi*V*0.008^2πV0.0082.

In 20 sec20sec the amount of water going through this facet is 20 times larger and equals to 30 l30l (this equals to 0.03 m^30.03m3) since there are 1000 liters in one cubic meter).

So, we have an equation with one unknown V(m/sec)V(msec):
pi*V*0.008^2*20 = 0.03πV0.008220=0.03
Solution of this linear equation (speed the water leaves the facet in m/sec) is
V = 7.46 m/secV=7.46msec

Personally, I think that this is a very high speed and the numbers in this problem might not be practical.