Plumbers physics?

[Stevey]

This should sort out the wheat from the chaff

I'm trying to understand how to manipulate water pressure using this equation:

p=F/A

where: p=pressure
F=Force
and A=Area




1. How do I find the (p) pressure? and what is it measured in?

2. How do I find (F) the value of force? and what is it measured in?

3. And (A) is the area of what? The cross section of the 22mm pipe, the 1m2 tank, or what?




My Example:

I have a water tank of 1 cubic metre capacity, which has a mass of 1 Ton or 1000 kilos or 100000 grams.

The tank has an open ended 22mm pipe exiting its base, 1 metre in length.


Question 1. What is the water, that is flowing out of the 22mm pipe measured in: pressure units/force units/metres per second/newtons?

Question 2. If I were to double the size of that water tank to 2m3, ie 2 Tons of water, would that extra Ton of mass make the water exiting the 22mm pipe, exit faster? would the pressure and/or the force of that exiting water increase?


I have more questions, but I just want to get my head around these points first.

Thanks for your help, and all the best for the new year!

 

[ChrisR]

EAsy -
Pressure in Pascals
Area in square Meters
Force in Newtons.
1 Newton per square Metre - 1 Pascal.

Q1 , Pressure where?
Q2 Force downwards on the bottom of the tank
From Force = Mass x Acceleration
f = 1000 x g
where g is 9.81 metres per second squared, the acceleration due to gravity.
That's spread over the whole of the bottom of the tank.

So pressure on the bottom
= 1000 x 9.81 / tank area, in Pa.

Area of the bottom depends on the shape and it comes out that the pressure = the height of the water inthe tank. Usually measured in Bar , 9.81 metres = 1 Bar, = 100kPa.

Lateral pressure at a small point on the side, depends how deep you measure it.

Q3 , per unit area, = 1 square meter.

 

[lightning]

i would say for example

a container 1m2 and 1m high would contain 1000 litresof water of mass 1000kg

so the 1000kg of water would weigh 1000x9.81 =9810 newtons per square meter{9.81kn/m2}

its not how big the container its how high the container is

greater the head the greater the pressure.

is that what you are after

 

[sooey]

And this all goes to prove that Chrisr is faster than lightning.

 

[lightning]

damm that was because i was checking my spelling.

 

[doitall]

And this all goes to prove that Chrisr is faster than lightning.

Still took 23 mins to look it up though

 

[ub7rm]

Pressure at the bottom of the tank = density of water x g x height of the water.

As previously mentioned, pressure is a function of the 'depth' of water not the volume, so it depends on the geometry of your tank. A tank with two tonnes of water (approx 2m3) spread out over an area such that the maximum depth was two millimeters would have no appreciable pressure whereas the same two tonnes stored in a tank which was 10m tall but extremely narrow would obviously give a much higher pressure.

Two extreme examples but they should make it easier to appreciate whats going on.

 

[gas4you]

All above my head If it works it works

 

[Stevey]

Damn, that was fast guys!! lol. Thanks for your replies. Pizzas burnin in the oven. Gonna chew over your replies while chewin over pizza.

Be back with more questions later or not if I understand things correctly....


Thanks again

 

[Stevey]

Sweet, I get it! pressure is a function of depth, and geometry of container.

So if I dropped a length of 22mm copper pipe 10 kilometres down to the bottom of the sea bed.
Then with an almighty pump, pumped out all the oceans for example, leaving just the 10k pipe stuck up in the air full of water.
If i removed my thumb to let the water out of the pipe, the water pressure exiting the pipe would equal the water presurre pressing down upon the seabed had I not drained the oceans??

Sounds a bit convoluted but this is correct, yes?

 

[Stevey]

The reason I ask, is that I was watching an old western. And in one of the scenes they were quarrying gold using a water blasting method... One guy trying to hang on to a 3 to 4 inch hose that ran up the hill, with the pipe getting bigger in diametre the further up the hill it ran.

Thinking that they wouldn't have had any mechanical pumps in those days, I wondered how they got enough presurre to blast away at the overburden.

 

[Stevey]

They must have Had some kind of tank or reservoire at the top of the hill. Like a cistern or something... is this how they did it?

 

[sooey]

A pint of clear water weighs a pound and a quarter. (And don't believe everything you see in old films)

 

[Stevey]

Is that a UK Pint or a Dry US Pint?

 

[Terrywookfit]

Capability Brown used the method of a reservoir and decreasing pipe sizes to power fountains!!

Obviously the jet of water would only rise to the level of the reservoir!!