Buoyancy and Archimedes Principle

advertisement
+
Buoyancy and
Archimedes Principle
Fluids Chp. 10
+
Buoyancy

Things seem lighter when submerged in water, this is
because the buoyant force of the water is assisting in
cancelling out some of the gravitational force. The mass of
the rock hasn’t changed, it just has an external Force working
on it, a very relaxing Force I might add.

The Buoyant Force is equal to the product of the density of
the fluid, the gravitational constant and the Volume of the
fluid displaced.
+
Consider this

Consider two pails filled to the brim. One pail contains only
water the other has water and a piece of wood floating in it.
Which pail has the greater weight?
+
Archimedes Principal
 States
that the buoyant force on an object
immersed in a fluid is equal to the weight
of the fluid displaced by the object.
+
THE SAME!

They have the same weight, the wood displaces a volume of
water equal to the weight of the wood. Archimedes principal!

I know, cool right.
+
Lets try this…

A 70kg ancient statue lies at the bottom of the sea. It’s volume
is 3.0 E^4 cm^3. How much Force is needed to lift it?

Remember…

Sea Water 1.025E^3 kg/m^3

Divide by 100 for each dimension (cm to m)

G=9.81 m/s^2
+
Answer
Fg-Fb=Force
to Lift
(686.7N-294.3N)=
[392.4N]
+