Gauge pressure at the bottom of a barrel

AI Thread Summary
The discussion centers on calculating the pressure at the bottom of a barrel containing a layer of oil and water. The correct formula used is the sum of the pressures from both the oil and the water, leading to the total pressure at the bottom. Initially, there was confusion about whether to treat the pressure of the water as a negation of the oil's pressure, but this was clarified. The key takeaway is that both fluids contribute to the pressure at the bottom, and understanding the context of the problem is essential. Attention to detail in reading the question is crucial for accurate problem-solving.
Of Mike and Men
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Homework Statement


A barrel contains a 0.110 m layer of oil and a density of 690 kg/m3 floating on water that is 0.300 m deep. What is the pressure at the bottom of the barrel?

Homework Equations

The Attempt at a Solution



Poil + Pwater = Ptotal

My question is why am I using this formula? I got the correct answer, but initially I wanted to treat the pressure of the water as a negation of the pressure of the oil, causing the barrel to float. So, Poil - Pwater. Is the reason for the addition because I am treating the bottom of the barrel as a point and the pressure acting on it in every direction equally and taking my gauge pressure from that exact point?

Thanks
 
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Of Mike and Men said:
My question is why am I using this formula? I got the correct answer, but initially I wanted to treat the pressure of the water as a negation of the pressure of the oil, causing the barrel to float.

My reading of the question is that both the oil and the water are in the barrel.
 
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CWatters said:
My reading of the question is that both the oil and the water are in the barrel.
Okay, thank you. I mis-read that. I was assuming the barrel was floating on the water. Paying attention to sentence structure is useful. ?:)
 
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