# Water in engineering questions

1. Apr 5, 2014

### dimens

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

See attached.

2. Relevant equations

3. The attempt at a solution
The first question, I think it's going upwards because the pressure on the bottom is higher, but I'm not sure the relevant equations to help prove it.

For the second question I'm also pretty lost.

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2. Apr 5, 2014

### SteamKing

Staff Emeritus
1. When posting HW problems, it is recommended that only one problem per thread be used, to eliminate any confusion in providing hints or explanations.

2. Regarding your first problem: Assume you have a bucket of water which is perfectly still. Is the pressure at the bottom of the bucket higher a.) at the surface of the water, or b.) at the bottom of the water in the bucket?

3. Regarding your second problem: Have you heard of a.) Bernoulli's Principle, b.) Torricelli's Law, c.) both a. and b., d.) neither a. nor b.?

http://en.wikipedia.org/wiki/Bernoulli's_principle

http://en.wikipedia.org/wiki/Torricelli's_law

3. Apr 5, 2014

### dimens

1. I'll keep this in mind next time.

2. It's highest at the bottom of the water in the bucket. Pressure increases with depth? Thus the water is going down?

3. I've heard of Bernoulli's briefly but not Torricelli's.

4. Apr 5, 2014

### SteamKing

Staff Emeritus
You seem surprised. How much study about fluids have you done? Remember, the bucket was sitting still with the water inside. The water was not moving up or down.

Then you need to become much better acquainted with Mr. Bernoulli and especially with Mr. Torricelli.

5. Apr 5, 2014

### dimens

so within a pipe. The place with the higher pressure suggests it's going towards that pressure.

Low pressure ----> High presure
Most definitely. I'll have to read tonight. One week missed in uni and I'm paying for it. Lol

6. Apr 6, 2014

### SteamKing

Staff Emeritus
Not necessarily. A fluid like water can be sitting still in a bucket, not moving at all, and still develop a pressure gradient throughout its depth. The point I am trying to show you is that all differences in pressure in a fluid are not necessarily the result of movement of a fluid in a pipe or any other container.

Once you have studied Bernoulli's equation, you will see that the pressure at one point in a moving fluid can drop, but the velocity of flow increases in order to keep a balance in the total amount of energy contained inthe flow.