# Easy Physics Concept but I cannot understand

1. Apr 22, 2012

### jmk193

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

Fluid is flowing from left to right through a pipe (see the drawing). Points A and B are at the same elevation, but the cross-sectional areas of the pipe are different. Points B and C are at different elevations, but the cross-sectional areas are the same. Rank the pressures at the three points, highest to lowest.

I could not attach the image but it looks like this: [ A ]---B--- , where A is thicker than B, and C is way above these two. The answer is A,B,C.

2. Relevant equations

P = F/A
Bernoulli's Equation maybe?

3. The attempt at a solution

I understand that Point C has the lowest pressure because it is elevated. To decipher between A and B, I am using the equation P = F/A. However, this tells me that pressure and area are inversely proportional which would suggest that Point A has a lower pressure than Point B. Where is my logic wrong?

2. Apr 22, 2012

### LawrenceC

When you say A is thicker, what do you mean? Larger in internal diameter?

3. Apr 22, 2012

### jmk193

yes A is larger in diameter than B.

4. Apr 22, 2012

### LawrenceC

So what can you say about the velocities at A and B?

5. Apr 22, 2012

### jmk193

The velocity at Point B will be greater than the velocity at Point A because area and velocity are inversely proportional according to A1v1 = A2v2.

6. Apr 22, 2012

### LawrenceC

Now looking at Bernoulli's equation, what does that tell you about pressures at A and B?

7. Apr 22, 2012

### jmk193

I see it now!!! Thank you so much!!!!!!!