How could spring water lift a person?

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Homework Help Overview

The discussion revolves around the physics of how spring water could lift a person to a height of about 4 meters, as depicted in a TV advertisement. The subject area includes concepts related to fluid dynamics, forces, and the impulse-momentum theorem.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the feasibility of spring water lifting a person, questioning the necessary conditions such as the height of the water source. Some engage in calculations related to the velocity of the water and its implications for lifting a weight.

Discussion Status

The discussion is active, with participants sharing their calculations and interpretations. There is a mix of numerical analysis and conceptual exploration, with no explicit consensus reached on the methods or conclusions. Some participants express confusion about the reasoning of others, indicating a dynamic exchange of ideas.

Contextual Notes

Participants note the importance of the water table's height relative to the ground level and question the practicality of the scenario presented in the advertisement. There are references to specific calculations and assumptions about the water's velocity and its ability to lift a weight.

scalar
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In an TV advertisement, a young man was lifted by an artificial spring water to a height about 4 m. Supposed the man's weight is 800N, and the sectional area of the spring water is 0.2*0.2 m^2, and using the impuse-momentum theorem, I got a velocity of the spring water of 4m/s.
Is this correct?
 
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As long as the water table of the spring at its source was more than 4m above the ground where the man was standing, you're good to go, and you don't need all those fancy calculations.
 
scalar said:
In an TV advertisement, a young man was lifted by an artificial spring water to a height about 4 m. Supposed the man's weight is 800N, and the sectional area of the spring water is 0.2*0.2 m^2, and using the impuse-momentum theorem, I got a velocity of the spring water of 4m/s.
Is this correct?
I don't quite understand what Dave is saying.

I get 4.5 m/sec at the height where the man is located. [itex]F = vdm/dt = v\rho dV/dt = v\rho Av = \rho Av^2[/itex]. What is the velocity at the ground level?

AM
 
Andrew Mason said:
I don't quite understand what Dave is saying.
I was second-guessing him. I was assuming he wanted to figure out whether it was practically possible for a volume of water to lift a man 4 metres, (after all, that's what his thread title implies he's asking about), but that his method for doing so was with numbers (calcing the speed and momentum of the water) rather than deduction.

I was merely pointing out that, if the (inexhaustible) supply of the spring water was higher than ground (i.e. at least 4m higher) where the man is standing, then is is trivial to show that the water will shoot that high.
 
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aha, just as dave said, I'm discussing the posibility of the advertisement. And the method I used is the same as Andrew's. The velocity of the spring water at the ground is about 10m/s. Thank you all.
 
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