# B Pressure exerted by an ideal gas

1. Sep 20, 2017

### PainterGuy

Thank you.

In both cases, Fig 1 and Fig 2, error tolerance is the same. Also the pipe diameter and flow rate is the same in both cases. The only difference is length - in Fig 1 it's 1 km and in Fig 2 it's 2 km. In comparative terms, would it affect the height of water column in Tower 1, Tower 2 and Tower 3 in Fig. 2 compared to Fig 1? Thank you.

2. Sep 20, 2017

### jbriggs444

There is no way to know from the limited information that you have provided.

Given the flow rate that you have not specified, the pipe diameter that you have not specified and the viscosity of water which you can look up, how much pressure drop would the Poiseuille equation call for?

https://en.wikipedia.org/wiki/Hagen–Poiseuille_equation

Last edited: Sep 20, 2017
3. Sep 20, 2017

### PainterGuy

Thank you.

The Hagen–Poiseuille equation is ΔP=(8μLQ)/(πR⁴) and ΔP is is the pressure difference between the two ends. I think that "the two ends" don't refer to the two ends of pipe. Could ΔP be defined as the pressure difference between two points along the pipe? Thanks.

4. Sep 21, 2017

### jbriggs444

Yes.

You seem strangely resistant to providing numbers or doing calculations. Say you drop three diameters off of each end of your one kilometer pipe. Can you apply Poiseuille's equation to that length?

5. Sep 21, 2017

### PainterGuy

Thank you.

Is it okay? Please let me know. Thanks.

#### Attached Files:

• ###### Poiseuille1.jpg
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6. Sep 24, 2017

### PainterGuy

Hi @jbriggs444,

Could you please confirm if the calculation is correct? Thank you.