# Homework Help: Pressure gauge

1. Jun 10, 2009

### brunettegurl

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

Water flows at 3.64 L/s through a horizontal pipe that narrows smoothly from 10.2 cm diameter to 4.89 cm diameter. A pressure gauge in the narrow section reads 47.0 kPa. What is the reading of a pressure gauge in the wide section?

2. Relevant equations

F=PA

P1+ $$\rho$$gh+0.5*$$\rho$$V2=P2+$$\rho$$gh+o.5*$$\rho$$V2

3. The attempt at a solution

so first thing i did was convert 3.64L/s to 3.64x10-3 m3/s
and then found the area of each part of the opening. since they tell me the gauge reading at the narrow end (4.89cm) i used F=PA to find the force. using this force and the area of the wide end (10.2cm) i got a P. this was wrong..can someone tell me what i'm doing wrong??

2. Jun 10, 2009

### tiny-tim

Hi brunettegurl!

(have a rho: ρ )

I'm confused … what does force have to do with it?

Use conservation of mass to find the speeds, and then use Bernoulli's equation

3. Jun 10, 2009

### brunettegurl

thanks i realized that after i redid what i did