# Physics-Bernoulli's Equation

1. Jul 20, 2010

### Noles1

1. The problem statement, all variables and given/known data
A horizontal water main with a cross-sectional area of 184 cm2 necks down to a pipe of area 45.0 cm2. Meters mounted in the flow on each side of the transition coupling show a change in gauge pressure of 70.0 kPa. Determine the flow rate through the system, taking the fluid to be ideal.

2. Relevant equations
p+(1/2)rho*v^2+rho*gy

3. The attempt at a solution
I'm confused about how to do this problem without any velocity given. Thank-you!!

2. Jul 20, 2010

### 6Stang7

You need to solve for flow rate, so I ask, how would you represent flow rate in equation forum? When you apply Bernoulli's Equation, what are your unknowns? What do you know about the flow rate through the system given that the fluid is ideal?

3. Jul 25, 2010

### physx_420

set bernoulli's equation equal to zero and solve for v. Now since this is an ideal fluid the velocity of fluid flowing through point a, 1.84m, is going to be equal to the velocity of fluid through point b, 0.45m. So you then use the equation for volume flow rate which is
dV/dt= A1v1= A2v2, where A1 and A2 are the cross-sectional areas at point a and b, respectively.

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