A cylinder full of water with two holes at different heights

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Homework Help Overview

The discussion revolves around a physics problem involving a cylinder filled with water that has two holes at different heights. Participants are exploring the application of Bernoulli's principle and equations of motion to analyze the flow of water from the holes.

Discussion Character

  • Exploratory, Mathematical reasoning, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to derive equations for the height and distance related to the water flow using Bernoulli's principle and parabolic motion. Some participants question the validity of the approach and express uncertainty about the results.

Discussion Status

Several participants affirm the original poster's approach, indicating that the equations seem reasonable. There is a discussion about the simplification of expressions involving the velocities at the holes and their relation to the heights. While there is no explicit consensus, the conversation suggests a productive exploration of the problem.

Contextual Notes

Participants are considering the implications of their equations and the assumptions made regarding the flow and heights involved. There is an acknowledgment of the need for clarity on the relationships between the variables.

ValeForce46
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Homework Statement
To the sides of a container full of water there are two holes with a section negligible compared to the section of the base respectively at a distance of ##h_1=20 cm## and ##h_2=80cm## from the free surface of the water. Assuming that the tap pumps water in the container keeping constant the level of the liquid while water comes out from the holes and knowing that the two jet of water touch the ground in the same point (see picture), determine:
a) The height ##h## of the container;
b)the distance ##d## from the wall of the cylinder in which the holes are drilled and the point of the ground touched by the jets.
Relevant Equations
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Annotazione 2019-09-02 205206.png

This is what I did:
I know that ##v_1=\sqrt{2gh_1}## and ##v_2=\sqrt{2gh_2}## thanks to Bernoulli's principle.
Using equations of parabolic motion I get
##h-h_1-\frac{1}{2}g(\frac{d}{v_1})^2=0## and ##h-h_1-\frac{1}{2}g(\frac{d}{v_2})^2=0##. This means I have two equations in two unknowns ##h## and ##d##.
That's it? I feel like I'm totally wrong but I don't see other ways... (I checked dimension of both results)
the results are
$$d=\sqrt\frac{2(h_2-h_1)}{g(1/v_1^2-1/v_2^2)} = 0.8 m$$
and the height ##h=1.0 m##
Just let me know if you think I'm right :)
 
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Looks OK to me.
 
Looks OK to me, too.

It's interesting to see how the expression ##d=\sqrt\frac{2(h_2-h_1)}{g(1/v_1^2-1/v_2^2)} ## simplifies if you make the substitutions ##v_1=\sqrt{2gh_1}## and ##v_2=\sqrt{2gh_2}##.

Likewise, ##h## has a simple expression in terms of ##h_1## and ##h_2##.
 
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TSny said:
Looks OK to me, too.

It's interesting to see how the expression ##d=\sqrt\frac{2(h_2-h_1)}{g(1/v_1^2-1/v_2^2)} ## simplifies if you make the substitutions ##v_1=\sqrt{2gh_1}## and ##v_2=\sqrt{2gh_2}##.

Likewise, ##h## has a simple expression in terms of ##h_1## and ##h_2##.
You’re definitely right. At the end I get
##d=...=\sqrt{4h_1h_2}=0.8m##
Thank you!
 

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