How to calculate water pressure on glass walls.

**XnSdVd** · 24th Nov 2006, 15:30

I've got something in the works, but need to know how to calculate the force 1kg of water exerts on the sides of a 10cm cube.

Is it simply a case of 1000g/5 = 200g per side? Since water is usually found flat on the ground when not in a container and in a state of equilibrium?

**hwchoy** · 24th Nov 2006, 16:49

no lah, its the weight of the water column divided by the differential surface area at a given depth. the bottom surface don't count, only the four sides. the pressure falls as you go up the water column that's why its a differential equation. now you know why those hydroelectric dams are thicker at the bottom and thinner at the top?

**ranmasatome** · 24th Nov 2006, 17:10

no lah...hahahaha.. so funny la you choy..

**hwchoy** · 24th Nov 2006, 17:11

simi funny? not calculate this way meh? pressure on glass depends on the depth mah.

**ranmasatome** · 24th Nov 2006, 17:23

yes.. correct.. but the way you say is funny lah..

**hwchoy** · 24th Nov 2006, 18:06

Originally Posted by ranmasatome

yes.. correct.. but the way you say is funny lah..

I'll wait at the airport and "help" you with all the fishes.

**valice** · 24th Nov 2006, 18:09

Let's organise a Justin (fish to be exact) welcome party at the airport...

Damn... This is so out-of-topic...

But seriously, I being a computer engineer, I have no idea how to do the calculation... Choy, care to elaborate more on the differential formula? Power 2 differential equation or just the simple one? It would be interesting...

**hwchoy** · 24th Nov 2006, 18:22

hey I am also computer science like you, but heck this is A level physics right?

but I don't know what kind of differential equation leh, I meant to tell him that you have to slice the depth parameter to an "infinitely" small instance and calculate the pressure there, which is the definition of differential calculus right? note I am speak from memory as old as you are

**XnSdVd** · 24th Nov 2006, 21:45

Well crap... i was hoping one of you would be able to give me the formula...

Now it's up to Thomas to show us the light.

**hwchoy** · 24th Nov 2006, 22:01

well if you know any guys who design hydro dams, I'm sure he'd know it by heart

**XnSdVd** · 24th Nov 2006, 22:06

We're on an Island master Choy... i don't think we'll find any. But strange that no one's asked considering everyone's afraid of their tanks breaking.

**ranmasatome** · 24th Nov 2006, 22:09

actually for such a small container.. why are you worried?? we arent building anything of epci proportions to require such calculations

**hwchoy** · 24th Nov 2006, 22:11

any civil engineer should know how to calculate, any retaining wall would entail similar calculations.

**XnSdVd** · 24th Nov 2006, 23:13

I'm asking because from the formula we can predict what will happen when i try to build a 5x1.25x1.25m tank.

**Shadow** · 25th Nov 2006, 00:03

check out this web site:

How to Calculate the Glass Thickness for your Aquarium:
http://saltaquarium.about.com/gi/dyn...ickness.0.html

or maybe this one

DIY Custom Aquarium Glass Thickness Calculator :
http://saltaquarium.about.com/cs/aqu...customtank.htm

**ranmasatome** · 25th Nov 2006, 09:56

you want to build that?? err..in your house?? err... by yourself?? err..ok.

**hwchoy** · 25th Nov 2006, 10:50

no problem lah, it only weighs seven tons.

**XnSdVd** · 25th Nov 2006, 13:58

Therefore, the question is really, how much force does 7812.5kg of water put on the sides of a container?

And yes, it will be constructed one day... ONE DAY. After i've graduated and started working and bought my own place that's not a HDB. It might never happen. But hey, knowledge is always useful.