Archimedes’ Principle
Abstract:
In this experiment, buoyant force was tested first by qualitatively observing the process
when a golf ball was lowered into a water filled bucket and also buoyant force as a function of
volume submerged was determined by lowering a wooden block into water. Then, using
Archimedes’ principle, the density of water was determined by changing the mass using
washers and observing the amount of water that was displaced and the density of given objects
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were identified at last by using a digital scale as the objects were lowered into the water bucket.
Using the data collected at the end of experiment, calculated density of water in experiment II is
1300
kg
m
3
and in experiment III is
1136
kg
m
3
.
Introduction:
The goal of this experiment is to understand buoyant force and to find the density of
water experimentally. This lab is also designed to understand Archimedes’ principle by
measuring the density of various unknown objects. Archimedes’ principle states that when an
object such as a ball is submerged in water, it experiences buoyant force in upward direction
which is equal to the weight of displaced fluid, so buoyant force can be described as
B
=
ρ
fluid
Vg.
Using Archimedes’ principle, it can be seen that if an object is denser than the
density of the water, then the object will sink with downward acceleration and if the object has
lower density than the water, then it will float. Lastly, if the object is in a resting position such as
floating without any acceleration, then the forces such as the weight of the object should equal
to the upward buoyant force.
Theory:
When the object was lowered in the water, it has an equal and opposite forces which are
buoyant force and the weight of the object acting on it, so

F
B

=
m g
Since the object is not moving nor accelerating, then the buoyant force must equal to all the
other forces acting on the object;
mg
=
ρ
water
V
submerged
g
m
=
ρ
water
V
submerged
Then, Archimedes’ principle can be written as;

F
B

=
ρ
water
V
submerged
g
Procedure:
Part I: Golf ball in water
This first part of the lab is to understand the relationship between the buoyant force versus the
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 Spring '08
 SAMPOGNA
 Physics, Force

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