Bernoulli's Equation on water hose

AI Thread Summary
The discussion focuses on applying Bernoulli's Equation to analyze water flow through a hose and nozzle system. The water speed through the nozzle is calculated to be 49.22 m/s based on the initial flow speed of 0.67 m/s in a larger diameter hose. For pressure calculations, the pressure at the pump is derived using the equation P1 + 1/2 D * V1^2 = P2 + 1/2 D * V2^2, with P2 set at 1 atm. Participants suggest converting all figures to SI units for accuracy and recommend using a reference table for unit conversions, specifically noting that 1 atm equals 101.325 kPa. This approach ensures clarity and consistency in the calculations.
maniacp08
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Water flows at 0.67 m/s through a 3.0 cm diameter hose that terminates in a 0.35 cm diameter nozzle. Assume laminar non-viscous steady-state flow.
(a) At what speed does the water pass through the nozzle?
49.22 m/s

(b) If the pump at one end of the hose and the nozzle at the other end are at the same height, and if the pressure at the nozzle is 1 atm, what is the pressure at the pump?
atm

I have found the answer for part A.
I have set up an equation for part B:
I have to find P1
P2 = 1 atm
v1 = .67 m/s
v2 = 49.22 m/s
let D = density of water = 1000kg/m^3

P1 + 1/2 D * V1^2 = P2 + 1/2 D * V2^2
P1 = P2 + 1/2 D * V2^2 - 1/2 D * V1^2
P1 = 1atm + 1/2(1000kg/m^3) * (2422.6084 m/s) - 1/2(1000kg/m^3) * (.4489m/s)

How do I convert this or get answer for P1 in terms of atm?
 
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maniacp08 said:
How do I convert this or get answer for P1 in terms of atm?

Most of your figures are in SI units. So I'd recommend working in SI, then converting at the end if you need the answer in terms of atm.

Your table of information / equation table should give you 1 atm in SI units. (If you don't have one, find the table of information / equation table you'll have in your exam, print it out, and refer to it constantly, so that you get used to where everything is!)
 
1 atm = 101.325 kPa
 
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