experiment206.docx

8/10/2019 EXPERIMENT206.docx

1/3

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


2/3

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-


3/3

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

experiment206.docx

Documents