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Power of a pump

by duke_nemmerle
Tags: power, pump
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duke_nemmerle
#1
Apr13-08, 02:58 PM
P: 49
1. The problem statement, all variables and given/known data
Water is pumped steadily out of a flooded basement at a speed of 5.0 m/s through a uniform hose of radius 1.0 cm. The hose passes out through a window 3.0m above the waterline. What is the power of the pump?


2. Relevant equations



3. The attempt at a solution

I actually correctly solved the problem by taking advantage of the fact that
[tex] P = \frac{\Delta W}{\Delta t }[/tex] which for us is [tex] P = \frac{\Delta m}{\Delta t} (gh + \frac{1}{2}v^{2})[/tex]

My question is, if the force applied is constant, why can't I use [tex] P = \frac{F\Delta d}{\Delta t} [/tex] since it's a simple matter of finding the force and [tex]\frac{\Delta d}{\Delta t} = v[/tex] is given.
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luben
#2
Apr13-08, 03:21 PM
P: 68
hello duke, i think the force F you specify cannot be found without using Bernoulli equation.
duke_nemmerle
#3
Apr13-08, 03:36 PM
P: 49
Yeah, I had actually found the force using an equation that is only good for static fluids, I'm going to see if using Bernoulli gets me the same result both ways. Thanks :)


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