# Measurement Question.

1. Jul 5, 2008

### nickberg

First of all, this is not a homework question. This was a question on a test I wrote on friday for which I cannot find the information in any texts.

The following: "pressure exerted by a water column measured in feet of water or occasionally inches of water" is a good definition of:

1)pressure
3)density

I know that the measurement is something typical of a manometer, but I can't see how it would fit in any of the options above. Your opinions please.

2. Jul 5, 2008

### tiny-tim

Welcome to PF!

Hi nickberg! Welcome to PF!

3. Jul 5, 2008

### Redbelly98

Staff Emeritus
Re: Welcome to PF!

It's one of the specifications of a water pump. As I recall, it's either:

1. The height of the water in a tube connected to the pump's output, or
2. The maximum height this water can have, at which the pump's flowrate becomes zero.

A pump provides maximum flow at zero head. But in many situations (such as basement sump pumps), the water is pumped out through a tube which rises above the pump. That water produces a back-pressure on the pump, reducing the water's flow rate. Let the water rise high enough, and the back-pressure reduces the flow to zero. The maximum head should be enough to pump water from the basement floor to above ground level.

For example:

I don't understand what is being asked in post #1. nickberg, you say you wrote the question but do not understand how the question fits any of the options. Since you are the question author, why can't you come up with an answer that makes sense to you? What am I missing here?

Last edited by a moderator: May 3, 2017
4. Jul 5, 2008

### tiny-tim

Re: Welcome to PF!

What?? :rofl:

(why are you answering anyway? how does that help the OP? )

5. Jul 5, 2008

### Xezlec

Re: Welcome to PF!

I believe the answer to the original question is a head of water. This terminology is often used in the context of both pumps and hydroelectric generators to refer to the height/pressure difference of the water between the two reservoirs. It is useful, for example, to be able to say that certain kinds of turbines are more efficient for high head situations and others are better for low head.

I'm guessing maybe English is not his first language (am I right?) and he meant to say a test he took. Since you write down answers when you take a test, native speakers of other languages might possibly use the verb "write" to make "take". Maybe.

6. Jul 6, 2008

### Staff: Mentor

Re: Welcome to PF!

Yeah, other languages like British English.

7. Jul 6, 2008

### Xezlec

Re: Welcome to PF!

Oh, sorry, I didn't know that. Well at least I was right about what it meant.

8. Jul 7, 2008

### nickberg

That would be good old standard english. I'm Canadian and here you can "take" a test or "write" a test. They are interchangeable. Just like Americans say "zeee" and we say "zed", it still means the same thing. Thanks for the answers guys, it makes sense

9. Jul 7, 2008

### Redbelly98

Staff Emeritus
Re: Welcome to PF!

Wow, just when I thought I understood that language.