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Experiment 205
Archimedes Principle
PHY11L / B3 / Group 2Janolino, Bryan Austin H.
Abstract
The experiment made use of the
hydrometer in order to study Archimedes
principle. And to apply Archimedesprinciple in determining the density and
specific gravity of solids and liquids.
I. Introduction
Archimedes principle, physical law
of buoyancy, discovered by the ancientGreek mathematician and inventor
Archimedes, stating that any body
completely or partially submerged in a fluid
(gas or liquid) at rest is acted upon by anupward, or buoyant, force the magnitude of
which is equal to the weight of the fluid
displaced by the body. The volume ofdisplaced fluid is equivalent to the volume
of an object fully immersed in a fluid or to
that fraction of the volume below the surface
for an object partially submerged in a liquid.The weight of the displaced portion of the
fluid is equivalent to the magnitude of the
buoyant force. The buoyant force on a bodyfloating in a liquid or gas is also equivalent
in magnitude to the weight of the floating
object and is opposite in direction; the objectneither rises nor sinks. For example, a ship
that is launched sinks into the ocean until the
weight of the water it displaces is just equal
to its own weight.
II. Theory
Density is a characteristic physical
property of a substance. This means that no
two materials have the same density.
Density is mathematically defined as
Where: = density of the material
m = mass of the material
v = volume of the material
The unit of density is kg/m3 in MKS units
and g/cm3in cgs units.
Specific gravity is defined as the weight of
the body compared with an equal amount of
pure water at 4 degrees Celsius (4 C is thetemperature at which water is densest). It
also tells the number of times a certain
material is denser than water.
Specific gravity has no unit. The specific
gravity of a substance is the ratio of that
substance to the density of water.Mathematically:
Where: SGs= specific gravity of a substance
Ps= density of the substancePw= density of the water
III. Methodology
A.
Setup
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B. Materials
1 pc platform balance
1 pc hydrometer
1 set weights 2 pcs 250-ml graduated cylinder 3 pcs 250-ml beaker 1 pc cork 1 m string
2 pcs metal specimen
C. Procedure
A. Determining the Specific Gravity of an
Unknown Solid Sample Heavier than
Water
First, the group hanged the first metalsample at one side of a platform balance and
find its weight in air Wa.. After finding its
weight the group submerged the samplecompletely in a beaker of water and measure
its weight while it is in water Ww. The group
computed for the loss of weight of the
sample by the equation: loss of weight ofwater = WA WW. Then the group
determined the specific gravity by using the
equation: SG = WA / WA WW . The saidprocedures were repeated using the second
sample. After re-doing the procedures with
the new samples the group then compared
the experimental values with the actualvalues and then they identify the samples
used.
B. Determining the Specific Gravity of an
Unknown Liquid Sample
As of Part 2 of the experiment, the group
chose one of the metal samples used in part
A, its weight in the air WAwas used in this
part. The group then submerged the metalcompletely in the first liquid sample and
recorded its weight in the liquid, WL. The
group then computed for the loss of weight
of the body in the liquid with the equation:loss of weight of body in liquid = WAWL.
After determining the loss of weight of body
in liquid the group then computed for itsspecific gravity by the equation SG = WA-
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WL/ WAWW. The said procedures are then
repeated by the group using the second
liquid samples. They compared theexperimental values and actual values found
in table 1. After comparing they identified
the liquid samples. Then the grouptransferred the liquids into two separatethoroughly dried graduated cylinders to
proceed for the next part.
C. Determining the Specific Gravity of an
Unknown Liquid Sample using a
Hydrometer
The results in Part B are verified using a
hydrometer.
A hydrometer consists of a weighted
float and a calibrated stem that protrudes
from the liquid when the float is entirely
immersed. A higher specific gravity willresult in a greater length of the stem above
the surface, while a lower specific gravity
will cause the hydrometer to float lower.
D. Determining the Specific Gravity of a
Solid Lighter than Water
The group then obtained a piece of cork and
measured its weight WA. They chose one of
the metal samples used in part A and used itas a sinker. They hanged the cork from a
string and hanged the sinker just below it.
The group computed for the weight with justthe sinker under water WCA-SWand with both
sinker and cork under water, W(S+C)W. The
group computed for the loss of weight of the
cork by the equation loss of weight of cork =WCA-SW W(S+C)W. After computing for the
loss of weight of cork the group then
computed the corks specific gravity by the
equation: SG = W/ WCA-SW W(S+C)W.
IV. References
General Physics 2 LaboratoryManual
Principles of Physics 9th
Edition byHalliday, Resnick and Walker
http://www.wikipedia.org