Archimedes Principle Video Lecture - Class 9

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Archimedes principle we're all aware of
the fact that some objects float in
water while others sink let's look at a
balloon do you know what makes a balloon
float on water well it's the upward
force exerted by water that makes the
balloon float to experience this try
pushing the balloon underwater you will
feel an upward force that makes it
difficult to push the balloon down now
release the balloon it bounces back to
the surface what happens here is that
the applied force acts in the downward
direction pushing the balloon down but
the water exerts an upward force on the
balloon pushing it up this upward force
exerted by water in the balloon is known
as up trust or buoyancy and the upward
force is called the buoyant force have
you ever wondered why anion kneel sinks
while a huge iron ship floats on water
let's see the iron nail sinks as it is
solid and compact with less volume in
water and it's density is greater than
water thus the up thrust exerted by
water on the meal is less than the
weight of the nail this causes it to
sink an ion ship floats as it is hollow
filled with air and occupies more volume
in water and it's density is less than
water thus the up thrust exerted by
water on the ship is greater than the
weight of the ship letting it float
these examples indicate that the
magnitude of the buoyant force depends
on the volume V of the immersed part of
the body the density Rho of the fluid
and the acceleration due to gravity G
thus up thrust of buoyant force is equal
to V Rho G
in general an object experiences a loss
of weight in water due to the up thrust
and it is equal to the weight of water
displaced by it this is better answered
using the law of buoyancy also known as
the Archimedes principle named after the
Greek scientist who discovered it
Archimedes principle states that when an
object is immersed in a liquid the
apparent loss of weight of an object is
equal to the up thrust and this is also
equal to the weight of the liquid
displaced we see the uses of this
principle in our daily lives ever caught
a fish with a fishing line when pulling
the line you would have felt the weight
of the fish in water is lighter than
when the fish has surfaced say the
weight of the fish in water is 4 kilos
its approximate weight outside would be
5 kilos well the water level 2 has come
down this difference in the volume of
water level will equal the loss and
weight of the fish when in water that is
the weight of the fish when outside -
its weight when immersed in water equals
the loss in weight of the fish so the
loss on weight of the fish will equal
the weight of the decreased water this
is because the up thrust or buoyant
force is equal to the weight of the
decreased amount of water thus
Archimedes principle is verified certain
technologies today work based on the
Archimedes principle to name a few the
designing of ships and submarines
hydrometer is used to find the specific
gravity of liquid and lacto meters used
to determine purity of milk
things to remember the upward force
exerted by a fluid is called a thrust of
buoyant force up thrust a buoyant force
equals V ro G Archimedes principle
states that when a body is partially or
fully immersed in a fluid it experiences
an upward force that is equal to the
weight of the fluid displaced by it
Archimedes principle is also known as
the law of buoyancy
you
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