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Gail Shaw wrote:
> "Darren New" <dne### [at] san rrcom> wrote in message
> news:477ad72c$1@news.povray.org...
>> You are sitting in a canoe, in a swimming pool, holding a cannon ball in
>> your lap. You throw the cannonball overboard, and it sinks to the
>> bottom. Does the level of water in the pool go up, go down, or stay the
>> same?
>
> I believe it should stay the same.
>
>
Incorrect. Hint - The cannon ball sinks to the bottom. Think about
what was preventing it doing so before.
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Patrick Elliott wrote:
> It does get wetter, just *outside* the range of displacement from the
> pressure you apply to the sand. And, if you stand there long enough that
> the grains can rearrange to be less compacted, you *will* end up with
> your puddle.
Indeed, but that doesn't really explain why it dries out initially.
Contrast it with stepping in wet mud for example, or on a wet carpet.
(as far as I understand the phenomenon, by the way, I believe that your
explanation of why the puddle eventually forms is incorrect).
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Darren New <dne### [at] sanrrcom> wrote:
> You are sitting in a canoe, in a swimming pool, holding a cannon ball in
> your lap. You throw the cannonball overboard, and it sinks to the
> bottom. Does the level of water in the pool go up, go down, or stay the
> same?
A classic.
The answer can be deduced by thinking about volume and weight.
In the canoe the ball displaces an amount of water proportional to
the weight of the ball. In the water it displaces an amount proportional
to the volume of the ball.
So the question is basically reduced to: Which is denser, the cannonball
or water?
--
- Warp
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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
> So the question is basically reduced to: Which is denser, the cannonball
> or water?
>
That's where I was headed. Does the cannonball displace more
water "underwater" than in the boat, and the difference being
volume*(DENSITYcannonball-DENSITYwater)/DENSITYwater?
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Greg M. Johnson <pte### [at] thecommononethatstartswithycom> wrote:
> That's where I was headed. Does the cannonball displace more
> water "underwater" than in the boat
No, it displaces less when underwater because its volume is "less" than
its weight, when compared to the water.
--
- Warp
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Warp wrote:
> Greg M. Johnson <pte### [at] thecommononethatstartswithycom> wrote:
>> That's where I was headed. Does the cannonball displace more
>> water "underwater" than in the boat
>
> No, it displaces less when underwater because its volume is "less" than
> its weight, when compared to the water.
Right. And you know that *because* it sinks. The water level wouldn't
change if the thing you threw over floated.
--
Darren New / San Diego, CA, USA (PST)
It's not feature creep if you put it
at the end and adjust the release date.
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Darren New nous apporta ses lumieres en ce 2008/01/01 19:13:
> You are sitting in a canoe, in a swimming pool, holding a cannon ball in
> your lap. You throw the cannonball overboard, and it sinks to the
> bottom. Does the level of water in the pool go up, go down, or stay the
> same?
>
> (I've asked this of probably a dozen or more scuba dive instructors, and
> only one has gotten it right. The reasoning behind the correct answer is
> obvious once you hear it. I don't remember if I got it right when I
> heard it.)
>
The level will go down.
When in your hand, you displace a volume of water that have the mass of the
cannonball. When you drop it, the displace a volume of water egual to it's own
volume. The cannonball have a higher density than the water as it sink.
--
Alain
-------------------------------------------------
You know you've been raytracing too long when you wonder if ground fog or
athmosphere will look better for your company's market share pie chart.
Christoph Rieder
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Warp <war### [at] tagpovrayorg> wrote:
> Greg M. Johnson <pte### [at] thecommononethatstartswithycom> wrote:
> > That's where I was headed. Does the cannonball displace more
> > water "underwater" than in the boat
>
> No, it displaces less when underwater because its volume is "less" than
> its weight, when compared to the water.
>
> --
>
Rethinking.
Using symbols:
Ph20= density of water
Pfe= density of cannonball
Mball= mass of canonball
IN CANOE:
displacement = Mball /(Ph2o)
UNDERWATER:
displacement = Mball / (Pfe)
But I'm not even sure if that's completely right now.
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On Wed, 2 Jan 2008 12:32:33 EST, "gregjohn" <pte### [at] yahoocom> wrote:
>
>But I'm not even sure if that's completely right now.
In the boat the cannonball displaces its own mass of water. In the water the
cannonball displaces its own volume of water.
Do I need to go on? :)
Regards
Stephen
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gregjohn <pte### [at] yahoocom> wrote:
> IN CANOE:
> displacement = Mball /(Ph2o)
No. In the canoe the ball displaces an amount of water equal to the
weight of the ball.
> UNDERWATER:
> displacement = Mball / (Pfe)
In the water the ball displaces an amount of water equal to the
volume of the ball.
The amount of water which weights the same as the ball is larger than
the amount of water which has the same volume as the ball.
--
- Warp
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