### Author Topic: summer riddle  (Read 4927 times)

#### altosax

• Sr. Member
• Posts: 328
##### summer riddle
« on: July 25, 2002, 12:28:32 AM »
hi all friends,
read this summer riddle and try to solve it for your fun.

there is a man in a boat at the centre of a lake.
he also has a big stone in his boat.
if the man throws the stone into the lake,
the level of water will increase,
will decrease or will remain equal?

too hard? too simple?
let me know,
altosax.

#### lnminente

• Jr. Member
• Posts: 73
##### summer riddle
« Reply #1 on: July 25, 2002, 11:42:12 PM »
mmmhhhhhhhhh. I will try.

I think that it depends of the density of the stone in comparation with the density of the water.

But also depends of the area of the ground of the boat.

I'm thinking about replace de stone by one litre of water.

#### hpguru

• Sr. Member
• Posts: 257
##### summer riddle
« Reply #2 on: July 26, 2002, 06:03:56 AM »
Depends on how many fish his wife cooked for supper later that evening.

Facing each other,
a thousand miles apart.
Facing each other,
a thousand miles apart.

#### JakBeNymble

• Sr. Member
• Posts: 308
##### summer riddle
« Reply #3 on: July 26, 2002, 07:02:01 AM »
Hi Friends,

Just guessing, . . .uh, . . .I think the water level would increase. How much it would increase depends on the Mass of the stone. The stone would displace an amount of water equal to it's Mass.

Archimedes noticed that when he set down in his bath-tub to take a bath, as he set down some of the water would pour over the side of the tub. He measured it one day, and found that it was exactly the same amount as his own Mass. It didn't matter how much he weighted, it was the same amount as his "Surface Area".

So I think that the water level should raise in proportion to the surface area of the stone.

It sounded good anyways when I read about it off of an empty pack of Instant Oatmeal this Morning.
Have a Great & Wonderful Day Friends. And thankx for putting up with my non-coherent Meta-physical speculations, . . .lol!
"Jak"=:-)

#### JakBeNymble

• Sr. Member
• Posts: 308
##### summer riddle
« Reply #4 on: July 26, 2002, 07:20:18 AM »
Here's one to think on,

There are three men, a Father and his two twin sons. They want to cross the river. The boat only will carry 1000lbs. However, these are very huge men! The Father weights 1000lbs him-self, and his two twin sons weigh 500lbs each! How can they all get across the river??

They could have been "Poster Children" for "Weight-Watchers"

Have a Great Evening Y'All,
"Jak"=:-)

#### altosax

• Sr. Member
• Posts: 328
##### summer riddle
« Reply #5 on: July 26, 2002, 09:45:55 AM »
the italian version for the one proposed by jak is:

a farmer have to cross a river with his wolf, his sheep and his cabbage.
he can carry only one at times but the wolf will eat the sheep if they remain alone, and the sheep will eat the cabbage if they remain alone too.

you can solve this the same way of the one by jak.

altosax.

#### Arne

• Hero Member
• Posts: 778
##### summer riddle
« Reply #6 on: July 26, 2002, 10:08:09 AM »
I think the water level vil drop since when in the boat it will depend on it's weight and when at the bottom of the lake it will depend on it's volume.

Best wishes
Arne
Best wishes
Arne

#### JakBeNymble

• Sr. Member
• Posts: 308
##### summer riddle
« Reply #7 on: July 26, 2002, 05:20:18 PM »
Hi "Friends",

Good thinking ARNE! AltoSax I see the answer to Your Last riddle. Marcus Arilius said,"You have to ask what is it's nature, what is the thing in it's self". What is the Nature and the Appetite of the Wolf & the Sheep? I think therein is the answer revealed. I will remember this one and add it to my collection. Thankx for an enjoyable and thoughtful riddle.

Have a Great Day My Friends!
"Jak"

One From the Mountains:
If a racoon's Foot covers an acre of Ground, what would it's tail cover?

Edited by - JakBeNymble on 26 Jul 2002  18:22:40

• Jr. Member
• Posts: 93
##### summer riddle
« Reply #8 on: July 29, 2002, 12:47:53 PM »
The level remains the same because nomatter if the stone is in the boat or in the water, the mass of the stone remains equal in both situations, which will cause the same amount of water displacement (in the boat it is part of the total mass of the boat and ?ts water displacement).

#### altosax

• Sr. Member
• Posts: 328
##### summer riddle
« Reply #9 on: July 29, 2002, 08:23:28 PM »
ok friends,
it's time to post the solution of my riddle.

to address the solution, first imagine the man in the boat without the stone and sign the level of the water.
1. add the stone into the lake and sign the level 1;
2. add the stone into the boat and sign the level 2.

it is clear that the level 2 is higher than the level 1 because the stone in the boat displaces a volume of water equal to its weight (principle of archimedes), while the stone in the lake displaces only a volume of water equal to its own volume.

this means that the level of water will decrease when the man throws the stone out of the boat.
the difficult here is that this seems a problem of weight but is a problem of volume.

NOTE.
i've read some of your answers using mass instead of weight. because the gravity is the same both for the stone and the water, an equal quantity in mass is also equal in weight so the principle of archimedes is true both with mass or weight.
---------------------------------------------------------

now a new one similar to the first, that you can experiment in your kitchen

imagine to pour some water into a recipient but not to reach the edge.
then imagine to throw in it some ice cubes until the water reaches the edge.
(it is not important the number of ice cubes you add, but is important that you reach exactly the edge of the recipient.)
when the ice will be melted, the level of water will increase (going out of the recipient), will decrease or will remain equal?

i must admit, this is a bit more difficult than the first one, but you can try...

regards,
altosax.

#### Arne

• Hero Member
• Posts: 778
##### summer riddle
« Reply #10 on: July 29, 2002, 09:54:21 PM »
We now have the same type of matter H2O which encreases in volume when it goes into frozen stage. And I assume that it then will push the water level higer when it remains as frozen. As soon as it melts it will again have the same volumen/weight as the already liquid water and the level will decrease until "noramal".

I have not taken into consideration if some of the ice actually is floating above water level, but without looking it up, I guess it  will not be as much as it will change my answer so much that it will be the same level.

So I stand with my first guess = decrease.
Crossing fingers :-)

Best wishes
Arne
Best wishes
Arne

#### altosax

• Sr. Member
• Posts: 328
##### summer riddle
« Reply #11 on: July 30, 2002, 12:30:50 AM »
hi arne.
as i wrote:

quote:

this is a bit more difficult than the first one

if you think it will decrease, you have to explain better your deduction.
but it could also increase or remain equal. who knows.

<edit>: please, take this as a fun, all you here are my friends and i'm not here to teach anything.

altosax.

Edited by - altosax on 30 Jul 2002  01:36:11

#### Arne

• Hero Member
• Posts: 778
##### summer riddle
« Reply #12 on: July 30, 2002, 02:05:44 AM »
It is fun and I don't mind at all if I am wrong. I am having a problem here, though, since I am not sure how the fact that water contracts between 0 and 4 degrees Celsius, and expands 10% when freezing and also looses density. The water in the tube will be in the range 0-4 when mixed with ice.

It is 2:40 am and I am shrinking, and so is the brain level LOL I will stick with my first guess.

Best wishes
Arne
Best wishes
Arne

#### JakBeNymble

• Sr. Member
• Posts: 308
##### summer riddle
« Reply #13 on: July 30, 2002, 04:08:43 AM »
Hi "AltoSax",

I'm with ARNE, I think this is fun! Besides I try to learn something new everyday, . .I would rather learn from a Friend as someone I didn't know. And I believe it or not, You ALL are like Family to me!!

I think that the water will decrease as the cubes melt. The reason is that water is a "strange substance". It Expands when it freezes, so as it melts I think that it will take up less space than when it is in a Frozen state.
To those who would find that hard to believe, just forget to put Anti-freeze in Your car's radiator over a good cold Winter, and watch Your Radiator and Motor-block Burst and Crack when the water in it Freezes. Well, , . .don't actually do that, it was just for an illustration.

Take Care My Friends, and have a Great Day!
"Jak"

#### altosax

• Sr. Member
• Posts: 328
##### summer riddle
« Reply #14 on: July 30, 2002, 09:45:17 AM »
in the meantime you solve mine, post yours so i also will have something to play with.

to arne and jak: i hope you had fun trying, but you need to go in deep with this because it is not as the stone one. your answer could be right but your explanation is not acceptable. also, your answer could be wrong: you have to post the proof of your findings.