1.
How high a building could fire hoses effectively spray from the ground? Fire hose pressures are
around 1 MPa. It is also said that larger fire engine mounted pumps can deliver from 90-300
gallons per minute, and hoses can be as wide as 30 cm diameter.
Thanks!
Solution
In the above situation, we apply the Bernoulli principle to obtain,
P1 + p*u*u/2 + pgh = P2 + p*v*v*/2 + pgH
Let us assume ther reference level for the above equation to be the same as that of the hose and
also, water leaves the hose at very small velocity.
Hence, applying the above assumptions, we have:
P1 = P2 + pgH
Here, P2 will be the atmospheric pressure, and the P1 will be the pressure at the hose,
That is, H = (P1 - P2)/p*g
H = (1*10^6 - 1.01 * 10^5)/1000*9.81 = 0.899 * 10^3 / 9.81 = 91.64 metres
Further, for the extra information provided, we will have to take a non-zero initial velocity. Here
the velocity at which the hose is delivering the water would be (Quantity / Area of cross section
of the pipe)