1. Oct 27, 2016

### Dusty912

1. The problem statement, all variables and given/known data
. Your physics teacher has assigned you the task of building a water ba,rometer. You've learned that the pressure of the atmosphere can vary by as much as 5 percent from 1 standard atmosphere as the weather changes. (a) What minimum height must your ba,rometer have? (b) One stormy day the TV weather person says, "The barometer pressure this afternoon is low 29.55 inches." What is the height of the water in your barometer?

2. Relevant equations

I'm not really sure where to even begin
3. The attempt at a solution
I have none, don't know where to start. There is no mention of a barometer in my textbook.

2. Oct 27, 2016

### Bystander

If I say to you, "Inches of mercury," does it ring any bells?

3. Oct 27, 2016

### Dusty912

not really. I mean I know that barometers use mercury.

4. Oct 27, 2016

### Staff: Mentor

Perhaps do a little browsing/research on the web? There are lots of articles that discuss barometers and how they work. I suspect that the question is asking about a simple sealed-tube barometer (tube sealed at top end, filled with fluid and standing open-end-down in an open container of the same fluid).

5. Oct 27, 2016

### Dusty912

okay so how would the atmosphere differing up to 5% be related to the height of the barometer?

6. Oct 27, 2016

### Dusty912

would this require taking a derivative?

7. Oct 27, 2016

### Staff: Mentor

What holds up the column of fluid in a barometer? What forces (or pressures) are balanced?

No. Just some calculations of pressures (air and fluid).

8. Oct 31, 2016

### andrevdh

A barometer measures air pressure.
It does so by balancing the air pressure with the pressure exerted by a column of fluid.
When to two pressures are equal the height of the fluid column is an indication of the ambient air pressure.

9. Oct 31, 2016

### Dusty912

got it, thanks for the help everyone!