Pressure at Points: What Does the Bernoulli Equation Tell Us?

[werson tan]

Homework Statement

isn't that p1 and [2 at the same point ? why shouldn't the P1 = P2 , which is
ρg(h1 +h2 +h3) ?

Homework Equations

The Attempt at a Solution

 

[BvU]

The velocity of the liquid makes a difference! Bernoulli.

 

[werson tan]

The velocity of the liquid makes a difference! Bernoulli.

can you explain further?

 

[SteamKing]

can you explain further?

BvU means you must apply the Bernoulli equation to the two points to find out what the pressures are at those locations.

When the fluid is in motion, the pressure at any point is no longer equal to just the static pressure.

 

[werson tan]

BvU means you must apply the Bernoulli equation to the two points to find out what the pressures are at those locations.

When the fluid is in motion, the pressure at any point is no longer equal to just the static pressure.

can you explain how to apply the Beroulli's pronciple so that the P1 = pg(h1 +h2) ? but not P1 = pg(h1 +h2+h3) ?

 

[BvU]

Have you learned about Bernoulli already ? This is a very straightforward application!

 

[werson tan]

Have you learned about Bernoulli already ? This is a very straightforward application!

maybe there are some points that i have left out , can you point out please?

 

[Chestermiller]

maybe there are some points that i have left out , can you point out please?

Please write out the Bernoulli equation for us (if you know it)?

 

[werson tan]

P +z + (v^2) /.2g , wher v = velocity

 

[Chestermiller]

P +z + (v^2) /.2g , wher v = velocity

Please try again. This is not an equation. I know this, because I don't see an equal sign. I also don't see any density in the equation. None of the terms in the equation are dimensionally consistent with one another. Please look it up and get it right this time. Otherwise, you won't be able to solve your problem.

 

[werson tan]

Please try again. This is not an equation. I know this, because I don't see an equal sign. I also don't see any density in the equation. None of the terms in the equation are dimensionally consistent with one another. Please look it up and get it right this time. Otherwise, you won't be able to solve your problem.

it should be P/ y + z + (v^2) /.2g , where v = velocity , y = ρg

 

[BvU]

This is almost comical: 0084.png in post #1 says it all but apparently isn't acceptable for Werson. Do you find it difficult to understand the term with $v^2$ in the Bernoulli equation ?

(What Chet means is that this expression is a constant)

 

[Chestermiller]

it should be P/ y + z + (v^2) /.2g , where v = velocity , y = ρg

This would be correct if that expression were set equal to a constant, and if that 0.2 in the denominator were a 2. Do you agree?

 

[werson tan]

This would be correct if that expression were set equal to a constant, and if that 0.2 in the denominator were a 2. Do you agree?

how to relate it to the P1 ? why not P1 = P2 , which is ρg(h1 +h2 +h3) ?

 

[Chestermiller]

how to relate it to the P1 ? why not P1 = P2 , which is ρg(h1 +h2 +h3) ?

Let's try to apply the Bernoulli equation to P1 and P2 to see what it tells us about their relationship. But, before doing that, do you understand the Bernoulli equation? Also, precisely what does z represent in the Bernoulli equation?

 

[werson tan]

Let's try to apply the Bernoulli equation to P1 and P2 to see what it tells us about their relationship. But, before doing that, do you understand the Bernoulli equation? Also, precisely what does z represent in the Bernoulli equation?

z represent the difference in height between 2 points

 

[Chestermiller]

z represent the difference in height between 2 points

You should think of z more as the elevation above a specified datum z = 0. In this problem, a logical choice for the datum would be the center of the pipe. Now please articulate what the Bernoulli equation means to you, or what each of the terms in the equation means physically.