Kinetic energy of water pouring

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Homework Help Overview

The discussion revolves around calculating the kinetic energy of water flowing from a faucet, specifically focusing on the amount of water poured over a set duration. The original poster provides detailed calculations based on the volume of water and its flow rate, questioning the results in relation to their expectations of kinetic energy from high-pressure water flow.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate kinetic energy using volume, mass, and velocity derived from the flow rate. Some participants question the relationship between kinetic energy and potential energy when dropping water from a height, while others seek clarification on the energy distribution in the system.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of kinetic and potential energy. Some guidance has been offered regarding the equivalence of energy from height versus flow, but no consensus has been reached on the original poster's calculations or assumptions.

Contextual Notes

The original poster expresses concern about posting in the correct section and mentions that the problem is not a formal homework assignment, which may influence the nature of the responses and the depth of discussion.

kox
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Hello. It's not a homework but it is kind of exercise. I was wondering what's the kinetic energy of water flow (for a certain amount) from a faucet. But I'm not sure if I got it right. So I counted how much volume of water is dropped in 30 seconds. It turned out it's about 5.6liters.
m=5.6kg // as 1 liter of water is almost 1kg
t=30s
l=1.256*10E-3m^2 // area of water dropping, cross-sectional area
Vol=5.6*10E-3m^3 // volume of water
Ek=mv^2/2
v=s/t
s=Vol/l
s=5.6*10E-3/1.256*10E-3 [m^3/m^2=m]
s=4.45m
v=4.45m/30s
v=0.148m/s
Ek=5.6kg*(0.148m/s)^2/2
Ek=5.6*0.0219kg*m^2/s^2
Ek=0.0613J
Ek=61.3mJ
So I got that pouring 5.6 liters of water realeses 61.3 milijoules. I thought it woul be a little more when I see water dropping at high pressure.
Did I get that right?
I don't know if I posted it in the right section. I'm ew here. It's not a homework but I'm afraid I would get my post deleted if I posted it in classic physics. Sorry I didn't use the template provided,but they didn't fit my post too good.
 
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The kinetic energy of slowly moving masses is tiny. You get the same kinetic energy if you drop the water by a height of just ~1mm.
 
I don't understand how is it equal to dropping water (how much?) from 1mm height? The water was dropping from more height and was at pressure. Could you explain?
 
In that case, some energy went to something else.

Dropping 5.6kg of water by a height of 1mm gives releases potential energy of mgh=5.6kg*10m/s2*0.001m = 0.056J = 56mJ.
 

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