http://www.yout
ube.com/watch?
v=y0SnFCs9z1g
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The question of why some objects sink
in fluids while others float can be
answered using the law of buoyancy.
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This law is known as Archimedes'
principle, after the ancient Greek
scientist who discovered it.
http://www.y
outube.com/
watch?v=ijj5
8xD5fDI
Archimedes Principle
It can be expressed as ‘Any object,
wholly or partially immersed in a fluid, is
buoyed up by a force equal to the weight
of the fluid displaced by the object.
 According to a tale, Archimedes
discovered this law while taking a bath.
After making this discovery, he is said to
have leapt out of his bathtub and ran
through the streets of Syracuse naked
shouting "Eureka!".
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If the weight of the water displaced is
less than the weight of the object, the
object will sink

An object will float, with the weight of the
water displaced equal to the weight of
the object.
It states that "any body partially or
completely submerged in a fluid is
buoyed up by a force equal to the weight
of the fluid displaced by the body.
 " The weight of an object acts
downward, and the buoyant force
provided by the displaced fluid acts
upward. If these two forces are equal,
the object floats.

If you’ve ever tried to push a beach ball
underwater, you’ve felt this principle in
action.
 As you push the ball down, it pushes
back up. In fact, a big beach ball can be
tough to hold underwater. As a physicist
in a bathing suit, you may wonder,
“What’s happening here?”

UNDERSTANDING QUESTIONS
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1. Who discover the principle of buoyancy?
2. How did he come up with the conclusion?
3. Explain the principle and use 3 examples,
with graphics.
4. What´s the opposite force to gravity (acts
upward)?
5. Is it the same if you talk about a ship with
cargo or empty? Yes /no? why?
6. g______, b_____ and density work together
to determine what floats your boat, or sinks
your ship