# Bernulli's equation

## Main Question or Discussion Point

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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Andrew Mason
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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
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 :)