# 15.6 pressure in a pipe

1. Apr 10, 2007

### iceman_ch

1. The problem statement, all variables and given/known data

Water flows at through a horizontal pipe that narrows smoothly from 10 cm diameter to 5.0 cm diameter. A pressure gauge in the narrow section reads 50 kPa.

What is the reading of a pressure gauge in the wide section

2. Relevant equations

A_1*F_1=A_2*F_2

3. The attempt at a solution

I tried to use this equation and it didn't work. I already know the answer is 5.34 x 10^4 but I need to know how to get that answer.

2. Apr 10, 2007

### denverdoc

Do you know bernoulli's eqn. I think that is what is needed here. Hint: in the narrow section the water must have 4 times the velocity as in the wide section. I'm off for now but maybe others can pick up if you need additional help.

3. Apr 10, 2007

### iceman_ch

Let me see if I have the equation correct.

P1-P2=1/2 (density) (V2^2-V1^2)

and

A1V1=A2V2

Is this what you are talking about?

4. Apr 10, 2007

### Mentz114

Yes. Those are correct. You can see the derivation here -

http://en.wikipedia.org/wiki/Bernoulli's_principle

5. Apr 10, 2007

### iceman_ch

Thanks for your help this make sense now