Who was Archimedes
Archimedes was a Greek scientist who discovered buoyancy
What is Archimedes Principle
As per Archimedes principle
When an object is immersed in a fluid
fully or partially
it experiences a upward force
This upward force is equal to weight of fluid displaced by the object
Example
Suppose we take glass
We full it to the brim with water
Now if we drop a coin into it
It leads to water falling from the glass
This is called water displaced from glass
As per Archimedes Principle,
the buyout force acting on coin is equal to
quantity of water which flows out of glass
Note
Buoyant Force remains constant After Object is fully immersed in water
Suppose we take a rock
We attach it to stretchable string
We note down the elongation(length of string)
Now we immerse string in beaker contain g water
Elongation(Length of string) decreases
This is because of buoyant force of water
More we immerse string in water,
Elongation(Length of string) decreases more and more
However when we immerse rock completely in water and bring it more down
The elongation does not decrease any further
This shows that
Buoyant Force remaions constant After Object is fully immersed in water
Different Uses of Archimedes principle
It is used in designing and manufacturing of
Ships and Submarines
Lactometer (a device to test purity or sample of milk)
Hydrometer (A divide to test density of different liquids)
Questions
NCERT Question 22 - The volume of a 500 g sealed packet is 350 cm 3 . Will the packet float or sink in water if the density of water is 1 g cm –3 ? What will be the mass of the water displaced by this packet?
