# pressure in BerBernoulli's equation!!!

Discussion in 'MCAT Study Question Q&A' started by peacefulheart, 12.19.12.

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1. ### peacefulheart

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In Bernoulli's equation: P+ pgh+ 1/2pv^2=K, is P gauge pressure or absolute pressure? thanks a lot.

3. ### HemorrageAmbrose 5+ Year Member

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Depends On the situation

4. ### milski1K member 5+ Year Member

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It is for absolute pressure.. If Pg=Pa+C where Pg - gauge, Pa - absolute and C just a constant and Bernoulli is true for Pa, you have Pg + Pg*gh + 1/2Pg*v^2 = Pa + C + Pa*gh + C*gh + 1/2Pav^2 + Cv^2 = K + C + C*gh + 1/2Pa*v^2 = K' + 1/2Pa*v^2

You end up with an extra term on the right side, proportional to Pa and v^2, which means that you cannot determine the whole relation solely based on Pg.