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huck
Joined: 19 Jan 2003
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 Posted: Fri Apr 27, 2007 4:03 am Post subject: A physics question for the geinuses out there |
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My villa (in haebongcheon) has a cement roof, which is quite large. Do you think it'll be able to support an inflatable pool, (12ft X 6ft) with 1-2 feet of water in it?
If you answer that, then you can go for question number 2...
If you were to weigh a circular pool that has a diameter of 10 feet, and 5 feet of water in it....
and then someone climbs into the pool, and lays on their back and floats on the water...Would the overall weight increase by however much the person weighs? |
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Drew345
Joined: 24 May 2005
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| Posted: Fri Apr 27, 2007 4:34 am Post subject: |
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Question 1.
Depends on where the building supports are. I wouldn�t try. Even waterbeds can cause damage and this is pool is way bigger.
Question 2.
The volume of water in a cylinder is h*Pi*r^2
For this pool, the volume is 5*3.14*25 or 393 cubic feet.
The weight is 24,500 pounds.
If you weigh 200 pounds and get in and float on your back, yes the total weight goes up to 24,700 pounds.
You float because the water pushes you up with a buoyancy force equal to the weight of water being displaced (Archimedes principle). So you float because the water is pushing you up by 200 pounds. So the water is pushing down on the building with a weight of the original weight plus your weight.
Drew |
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ttompatz
Joined: 05 Sep 2005
Location: Kwangju, South Korea
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| Posted: Fri Apr 27, 2007 4:34 am Post subject: Re: A physics question for the geinuses out there |
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| huck wrote: |
My villa (in haebongcheon) has a cement roof, which is quite large. Do you think it'll be able to support an inflatable pool, (12ft X 6ft) with 1-2 feet of water in it?
If you answer that, then you can go for question number 2...
If you were to weigh a circular pool that has a diameter of 10 feet, and 5 feet of water in it....
and then someone climbs into the pool, and lays on their back and floats on the water...Would the overall weight increase by however much the person weighs? |
1' deep = 72cu ft * 62.4 lbs/cu.ft = 4493 lbs.
2' deep = 144 cu ft * 62.4 = 8986 lbs.
circular pool = 392 cu ft = 24,492 lbs.
area of a circle = pi*r*r. 3.14*5*5
volume of the pool is area * depth (7805*5')
weight of fresh water = 62.4 lbs / cu.ft.
If someone climbs in the weight of the pool is increased by their weight. |
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tfunk
Joined: 12 Aug 2006
Location: Dublin, Ireland
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| Posted: Fri Apr 27, 2007 4:36 am Post subject: |
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I can't answer the first question because it depends on the structure supporting the roof.
The answer to your second question is 'yes'....the weight would be more or less evenly distributed over the area of the pool.
Last edited by tfunk on Fri Apr 27, 2007 4:37 am; edited 1 time in total |
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huck
Joined: 19 Jan 2003
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| Posted: Fri Apr 27, 2007 4:36 am Post subject: |
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you guys ARE geniuses...
thanks.. |
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tacon101
Joined: 31 Oct 2005
Location: seoul
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| Posted: Fri Apr 27, 2007 4:36 am Post subject: |
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dont know about the first one...probably also depends on the quality of the roof: age,thickness, quality
as for the second, of course if you weigh a bowl of water then put a fish in it and weigh it again, it will weigh more with the fish...your buoyancy doesnt affect your weight (gravity is still pulling) |
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tfunk
Joined: 12 Aug 2006
Location: Dublin, Ireland
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| Posted: Fri Apr 27, 2007 4:42 am Post subject: |
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| huck wrote: |
| you guys ARE geniuses... |
Sorry to be anal, but nerd is spelt with an 'n'. |
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Thunndarr
Joined: 30 Sep 2003
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| Posted: Fri Apr 27, 2007 5:38 am Post subject: Re: A physics question for the geinuses out there |
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| ttompatz wrote: |
| huck wrote: |
My villa (in haebongcheon) has a cement roof, which is quite large. Do you think it'll be able to support an inflatable pool, (12ft X 6ft) with 1-2 feet of water in it?
If you answer that, then you can go for question number 2...
If you were to weigh a circular pool that has a diameter of 10 feet, and 5 feet of water in it....
and then someone climbs into the pool, and lays on their back and floats on the water...Would the overall weight increase by however much the person weighs? |
1' deep = 72cu ft * 62.4 lbs/cu.ft = 4493 lbs.
2' deep = 144 cu ft * 62.4 = 8986 lbs.
circular pool = 392 cu ft = 24,492 lbs.
area of a circle = pi*r*r. 3.14*5*5
volume of the pool is area * depth (7805*5')
weight of fresh water = 62.4 lbs / cu.ft.
If someone climbs in the weight of the pool is increased by their weight. |
Dude. You have entirely way too much info crammed into your head. No offense. |
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ttompatz
Joined: 05 Sep 2005
Location: Kwangju, South Korea
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| Posted: Fri Apr 27, 2007 5:42 am Post subject: Re: A physics question for the geinuses out there |
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| Thunndarr wrote: |
| ttompatz wrote: |
| huck wrote: |
My villa (in haebongcheon) has a cement roof, which is quite large. Do you think it'll be able to support an inflatable pool, (12ft X 6ft) with 1-2 feet of water in it?
If you answer that, then you can go for question number 2...
If you were to weigh a circular pool that has a diameter of 10 feet, and 5 feet of water in it....
and then someone climbs into the pool, and lays on their back and floats on the water...Would the overall weight increase by however much the person weighs? |
1' deep = 72cu ft * 62.4 lbs/cu.ft = 4493 lbs.
2' deep = 144 cu ft * 62.4 = 8986 lbs.
circular pool = 392 cu ft = 24,492 lbs.
area of a circle = pi*r*r. 3.14*5*5
volume of the pool is area * depth (7805*5')
weight of fresh water = 62.4 lbs / cu.ft.
If someone climbs in the weight of the pool is increased by their weight. |
Dude. You have entirely way too much info crammed into your head. No offense. |
Nah... just a memory problem.... can't forget stuff fast enough
BUT
I'm not worth a damn at trivial pursuit.
No good trivia up there... just useless stuff. |
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tzechuk
Joined: 20 Dec 2004
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| Posted: Fri Apr 27, 2007 5:49 am Post subject: |
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We have a huge rooftop and we have a pool there in the summer.
We even have three small gardens up there!
I don't see why you would have problem with a pool. What we do though is that we empty out the water after we've used it - the water won't be any good the next time anyway because of leaves and other yucky stuff floating in it... |
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I'm Seoul Lost
Joined: 19 Jun 2006
Location: In the mountains of Gyeonggi
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tzechuk
Joined: 20 Dec 2004
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| Posted: Fri Apr 27, 2007 3:29 pm Post subject: |
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If my Korean chemical/mechanical engineer (majoring in viscosity, fyi) PhD husband says it's OK, who am I to argue?
I know water is heavy - I've done advanced physics myself - but note what I wrote once more: empty out the water when you are not using the pool. Having it for, say, an hour or two is not going to cause your roof to cave in.
One more thing:
The examples you've given are different from this case. The reason why those buildings/constructions collasped is because the water wasn't constant. It was flowing, so there was pressure which forced the water to burst the pipes/bridge. There's no pressure here to burst anything. You are not constantly pushing against the roof. So I say again, having a pool for an hour or two is not going to destroy your roof. |
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ttompatz
Joined: 05 Sep 2005
Location: Kwangju, South Korea
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| Posted: Fri Apr 27, 2007 4:31 pm Post subject: |
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| tzechuk wrote: |
If my Korean chemical/mechanical engineer (majoring in viscosity, fyi) PhD husband says it's OK, who am I to argue?
I know water is heavy - I've done advanced physics myself - but note what I wrote once more: empty out the water when you are not using the pool. Having it for, say, an hour or two is not going to cause your roof to cave in.
One more thing:
The examples you've given are different from this case. The reason why those buildings/constructions collasped is because the water wasn't constant. It was flowing, so there was pressure which forced the water to burst the pipes/bridge. There's no pressure here to burst anything. You are not constantly pushing against the roof. So I say again, having a pool for an hour or two is not going to destroy your roof. |
Actually, with the Sampoong department store collapse it was the changes in the structural supports in a concrete slab construction building that caused the problems and not specifically the water on the roof.
This would not be a water pressure issue but an issue dealing with the structural integrity of the supports to floor/roof in the roof and possible "punch-through" in a slab construction building.
In regards to the pool question specifically as posed by the OP, the 6X12x 1' deep pool would likely have no impact on a concrete slab constructed building (typical villa).
Last edited by ttompatz on Fri Apr 27, 2007 10:40 pm; edited 1 time in total |
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jdog2050
Joined: 17 Dec 2006
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| Posted: Fri Apr 27, 2007 6:21 pm Post subject: |
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| huck wrote: |
you guys ARE geniuses...
thanks.. |
I wouldn't try this in Korea...they are known for their ship-building capabilities...not so much for apartments. |
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n3ptne
Joined: 14 Sep 2005
Location: Poh*A*ng City
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| Posted: Fri Apr 27, 2007 7:19 pm Post subject: |
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If an object is floating, where does the weight excert itself?
More or less equally a long the bottom (because of displacement), if the object is in the center, and distributed between the wall, and bottom if the object is off center (depending on the area of the pool)?
Or, does gravity overcome the displacement and cause a great amount of weight to be excerted directly below the object? |
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