Bernoulli's Eq: P1=P2 & Torricelli's Eq

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Discussion Overview

The discussion revolves around the application of Bernoulli's equation in fluid dynamics, specifically in the context of fluid exiting a spigot and its relation to Torricelli's theorem. Participants explore the assumptions regarding pressure at different points in the fluid system.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why the pressures P1 and P2 are considered equal when applying Bernoulli's equation to fluid exiting a spigot, suggesting this leads to Torricelli's equation.
  • Another participant clarifies that in deriving Torricelli's theorem, it is assumed that both ends of the streamline are at atmospheric pressure, as they are exposed to the atmosphere.
  • A participant raises a concern about whether the pressure being referred to is internal pressure.
  • A later reply confirms that it is indeed the internal pressure of the fluid, but notes that at the points in question, this internal pressure must match the external atmospheric pressure.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the pressures involved in the application of Bernoulli's equation and Torricelli's theorem, indicating that the discussion remains unresolved regarding the interpretation of pressure in this context.

Contextual Notes

There are assumptions about the conditions at the ends of the streamline and the definitions of internal versus external pressure that are not fully explored or resolved in the discussion.

bluejay27
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When using Bernoulli's equation to describe fluid that is coming out from a spigot, why is it that P1 = P2 are the same? This cancellation will eventually lead to the Torricelli's equation.
 
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In deriving Torricelli's theorem, both ends of the streamline are assumed to be at atmospheric pressure. (They are exposed to the atmosphere.)
 
Isn't the pressure supposed to be internal pressure?
 
bluejay27 said:
Isn't the pressure supposed to be internal pressure?
Yes, it's the pressure inside the fluid. At those points that pressure must match the external atmospheric pressure.
 

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