Story by Vitruvius
of invention Archimed's law
| Hiero, after gaining the royal power in
Syracuse, resolved, as a consequence of his successful exploits,
to place in a certain temple a golden crown which he had vowed
to the immortal gods. He contracted for its making at a fixed
price, and weighed out a precise amount of gold to the
contractor. At the appointed time the latter delivered to the
king's satisfaction an exquisitely finished piece of handiwork,
and it appeared that in weight the crown corresponded precisely
to what the gold had weighed.
But afterwards a charge was made that gold
had been abstracted and an equivalent weight of silver had been
added in the manufacture of the crown. Hiero, thinking it an
outrage that he had been tricked, and yet not knowing how to
detect the theft, requested Archimedes to consider the matter.
The latter, while the case was still on his mind, happened to
go to the bath, and on getting into a tub observed that the more
his body sank into it the more water ran out over the tub. As
this pointed out the way to explain the case in question,
without a moment's delay, and transported with joy, he jumped
out of the tub and rushed home naked, crying with a loud voice
that he had found what he was seeking; for as he ran he shouted
repeatedly in Greek,
Taking this as the beginning of his discovery, it is said
that he made two masses of the same weight as the crown, one of
gold and the other of silver. After making them, he filled a
large vessel with water to the very brim, and dropped the mass
of silver into it. As much water ran out as was equal in bulk to
that of the silver sunk in the vessel. Then, taking out the
mass, he poured back the lost quantity of water, using a pint
measure, until it was level with the brim as it had been before.
Thus he found the weight of silver corresponding to a definite
quantity of water.
After this experiment, he likewise dropped the mass of gold
into the full vessel and, on taking it out and measuring as
before, found that not so much water was lost, but a smaller
quantity: namely, as much less as a mass of gold lacks in bulk
compared to a mass of silver of the same weight. Finally,
filling the vessel again and dropping the crown itself into the
same quantity of water, he found that more water ran over for
the crown than for the mass of gold of the same weight. Hence,
reasoning from the fact that more water was lost in the case of
the crown than in that of the mass, he detected the mixing of
silver with the gold, and made the theft of the contractor
perfectly clear. |
|
| Archimedes stated his law saying that "a
body, which is entirely or partially immersed in a fluid, receives a
lift in an upward direction from below with a force equal to the weight
that the given body moves".
On this picture, the object moves 100
cm³ of water and as a result experiences an upwards force of
100 gf. |
 |
How
can a boy drown a witch
...
a boy came to the river and
splashed to the other side. A witch run down to the bank.
Now she stays there and in a sweet voice speaks to the boy:
"Darling,
my darling, how can I get the next bank?”
"Hang
a heavy stone round your neck and go into water.”
The
witch did it, tied the stone round her neck, went into water and drowned ...
1.
What did the boy tell the witch
to do to get the other bank?
2. Why
do some objects sink in water?
3.
Why does a small nail sink in water but a heavy ship float?
4.
Why is a bucket of water easy to lift under
water and heavy in the air?
5.
Which forces operate
on the witch in water? Try drawing them.
How
can dog drown a turtle
...
At the end a codger dog was angry. Everything started to be too strange
for him and he went for a turtle. He caught
her at the right time. He was very angry and
decided he will kill her. But the clever turtle started
to plead with him and said that he could do anything with her, throw into the
fire but please do not drown her. Drowning she said was too terrible.
So the dog decided to throw the turtle into the water.
Hardly had the clever turtle touched the water, when she cried
to the dog:
"Silly
dog, I wanted it!”
And the dog was furious.
·
Questions of Physics
1.
Why do we sink?
What can we do against sinking
ourselves?
2.
What do you know about the density
of a human?
Can we breath and decrease our density
and so save us against sinking if we do not know to swim?
3.
If we were to swim in a
swimming pool on the Moon, would we feel the same upthrust as on the Earth or 6
times smaller?
4.
How could we make a submarine?
How is it possible that a submarine can float on the surface or under it?
5.
Is the Archimedes law valid in
the state of weightlessness?
Fragrant hair, a nationality Tay
...
A girl lives alone in the middle of forest. Once
she went to the river to bath. One of her hairs
fell out. She took it and said:
"My
fragrant hair, I will give you to the water.
Help me to find somebody there; somebody who I could
love.”
Then she gave a hair into the water.
A clear water played with the hair and carried it far away. The
thoughtful girl came back home. From this time day after day
she went back to the bank of the river and she looked at the river
level for a long time ...
·
Questions of Physics
1.
Will
an aluminum, phosphor,
asbestos, ice, drop of oil,
drop of mercury float in water?
2.
Will asphalt float in glycerine, and
a piece of
bakelite in the oil-fuel?
3.
Why does a hair float on
water?