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I'm trying to understand how exactly we can show that the pressure of a fluidxis lower or greater than the pressure of a fluidy. One good example I found is the following image.

Using Bernoulli's principle we can show that the pressure of an incompressible and steady fluid will decrease as the velocity increase. However, nothing tell us that the pressure of a moving fluidxis lower or greater than a stationary fluidy.

How can we explain this phenomena?

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Final answer:

Bernoulli's equation illustrates that for an incompressible, frictionless fluid, as velocity increases, pressure decreases, a principle demonstrated by examples such as shower curtains bulging and vehicles drawing close on a highway. This helps to understand pressure differentials in moving versus stationary fluids.

Step-by-step explanation:

Understanding Pressure Differences in Moving Fluids

When analyzing fluid dynamics, Bernoulli's equation is fundamental in explaining how pressure relates to fluid velocity. According to this principle, in an incompressible and frictionless fluid, there is a constant sum of the fluid's pressure, the fluid's potential energy per unit volume, and the fluid's kinetic energy per unit volume. From this equation, it can be derived that as the velocity of the fluid increases, the pressure within the fluid decreases, assuming the height remains constant. This is why in situations where fluid velocity increases due to narrowing of the channel, the pressure drops.

This phenomenon is observable in everyday life, such as with shower curtains bulging inward due to a lower pressure caused by the high-velocity flow of water and air, or vehicles being drawn toward each other as they pass closely due to the lower pressure in the air between them. Even though Bernoulli's equation does not directly compare the pressure between a stationary fluid and a moving fluid, we can deduce that if other conditions are equal, a fluid at rest would have higher pressure compared to a moving fluid where kinetic energy is higher.

It's important to note that Bernoulli's equation applies to a small volume of fluid as we follow it along its path. In real-life scenarios, there may be additional factors such as viscosity and turbulence which are not considered in Bernoulli's ideal fluid model. Nevertheless, Bernoulli's equation provides a useful framework for understanding the basic principles of fluid behavior.

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