Trouble with a basic fluid force problem

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Homework Help Overview

The discussion revolves around a fluid mechanics problem concerning the calculation of pressure on a horizontal surface submerged underwater. The original poster attempts to apply the formula for force due to fluid pressure but encounters a discrepancy between their calculated force and the expected pressure value.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the application of the force formula and the relationship between force and pressure. There is a discussion about the potential oversight of a factor in the calculations and the distinction between calculating force versus pressure.

Discussion Status

The conversation has highlighted a misunderstanding regarding the difference between force and pressure, with some participants confirming the original poster's realization. There is an acknowledgment of unit changes as a result of this distinction, suggesting a productive direction in clarifying the concepts involved.

Contextual Notes

Participants are navigating the definitions and relationships between force, pressure, and area in the context of fluid mechanics, with an emphasis on ensuring correct unit application.

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What is the pressure on a horizontal surface with an area of 2m^2 that is 4m underwater?

I tried to just use the formula: Force= (Density of water)(Area)(Depth)(gravity), plugging in the values Force=(1000kg/m^3)(2m^2)(4m)(9.8m/sec^2) and get 78400 N, when in reality the real answer is supposed to equal 39,200 N/m^2.
 
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I can confirm your answer. Maybe someone forgot a factor of 2?
 
Ahhh nevermind, I have been calculating the FORCE on the plate and not the PRESSURE on the plate which is P=F/A which would explain they I have to divide the force by 2.
 
Oh, good point. It also changes the units.
 

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