Why am I getting negative pressures when calculating Bernoulli's equation?

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SUMMARY

The discussion centers on the calculation of Bernoulli's equation, where the user encountered negative pressures on both sides of the equation. The issue was identified as a sign error in the derivation, specifically that the left side of the equation should be represented as -(p_2-p_1). This correction aligns with the principle that a decrease in pressure energy (PV) must equal the increase in kinetic and potential energy. The conversation also highlights the use of Slovenian language in the forum, which may pose challenges for some participants.

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71GA
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Hello i tried to calculate Bernulli's equation myself and i get negative pressures on both sides of equation. What am i doing wrong? It is all in a document.

Ty
 

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71GA said:
Hello i tried to calculate Bernulli's equation myself and i get negative pressures on both sides of equation. What am i doing wrong? It is all in a document.

Ty
First of all you are writing it out in Slovenian. That makes it a little difficult for most people to follow.

But it appears that you have done the derivation correctly except you have a sign switched. The left side of your equation third from the bottom of page 1 should be -(p_2-p_1). This is because the change in PV is equal and opposite to the changes in kinetic and potential energy: eg. A decrease in PV energy must be equal to the increase in the sum of changes in kinetic and potential energies.

oh, in mimogrede, dobrodošli v fiziki forumih

AM
 
Nice to see someone here also talks Slovenian :) And thank you. This was my first thread on this forum and i got a nice reply. That is why i now like this forum :)
 

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