Story by Vitruvius of invention Archimed's law
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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 |
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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?