Physics Laboratory 1

Archimedes' Principle

Objective:

In this lab students will verify Archimedes' principle by measuring the apparent loss of weight of several submerged objects and by finding the weight of the displaced fluid.  Students will also determine the density of the objects.  The PASCO Force Sensor together with the Science Workshop interface and the Data Studio software is used to measure the weights.

Theory:

For a theoretical treatment of Archimedes' principle, see the class notes.

Equipment:

Force Sensor
Two containers, one with and one without overflow spout
Various solid objects

Procedure:

Part I
Verify Archimedes' principle.

(a)  Determine the weight Wc of the empty container with the handle.  When the container is suspended from the force sensor, the force sensor measures the force of gravity (weight) acting on the object, and the program displays the magnitude of this force (in N) on the computer screen.
(b)  Determine the weight of an object Wo when it is suspended above the container with the overflow spout.  This container is completely filled with water, and the container with the handle standing below the spout is empty.
(c)  Determine the weight of the object Wow after it has been lowered into the water.   As the object is lowered into the water, water pours out of the overflow spout.  The container with the handle has collected this water.
(d)  Determine the weight Wcw of the container with the handle holding the collected water.
Determine these weights for four different objects and record the weights in a spreadsheet as shown below
 

Wc

Wo

Wow

Wcw

Ww

Fb

(Fb-Ww)/Fb

Object 1

              

Object 2

              

Object 3

              

Object 4

              

Data:

Click on a small picture if you want to see an enlarged picture.

  (a) (b) (c) (d)
Object 1: wpe7.jpg (29471 bytes) wpe1.jpg (29569 bytes) wpe3.jpg (30178 bytes) wpe5.jpg (30488 bytes)
Object 2: wpe7.jpg (29471 bytes) wpe9.jpg (29655 bytes) wpeB.jpg (29112 bytes) wpe11.jpg (29763 bytes)
Object 3: wpe7.jpg (29471 bytes) wpe15.jpg (29786 bytes) wpe17.jpg (29030 bytes) wpe19.jpg (29731 bytes)
Object 4: wpe7.jpg (29471 bytes) wpe1B.jpg (29656 bytes) wpe1D.jpg (27893 bytes) wpe11.jpg (29763 bytes)

For each of the objects:

Calculate the weight of the water that was displaced.  Ww=Wcw-Wc.  Record it in the spreadsheet.
Calculate the difference between the weight of the object in air and its apparent weight in water.  This difference yields the buoyant force Fb.  Fb=Wo-Wow.  Record Fb in the spreadsheet.
Compare Fb and Ww.  Calculate the percent difference=100%(Fb-Ww)/Fb and record it in the spreadsheet.

Part II
Determine the density of the objects used in part I.

Extend your Excel spreadsheet.
Set up labels as shown below.
 

mo

mw

Vw

ro

material

Object 1

          

Object 2

          

Object 3

          

Object 4

          
Determine the mass mo of each objects by dividing its weight by the acceleration due to gravity and record it in the spreadsheet.
From the weight of the water displaced by the object calculate its mass mw and record it in the spreadsheet.
Use the density of water, 1000kg/m3, and the mass of the displaced water, to calculate the volume Vw of the displaced water.  Record this volume in the spreadsheet.
The volume of the displaced water is the same as the volume of the object.  Calculate the density ro of the object  (r=m/V) and record it in the spreadsheet.
Compare the density you found with the density of the materials rt given in the table below.  Try to identify the material each object is made of.

 

Material Density (kg/m3)
Aluminum   2.7´103
Brass 8.7´103
Lead 11.3´103
Steel 7.9´103
Water 1.0´103

Open Microsoft Word and prepare a report using the template shown below.

Name:
E-mail address:

Laboratory 1 Report

In a few sentences summarize the experiment.

Show your spreadsheet entries from part I and part II.

Answer the following questions:
According to Archimedes' principle, the buoyant force is equal to the weight of the displaced fluid.  Do your experimental results verify Archimedes' principle?  Comment on your results.
Do your experimentally determined densities of the various materials agree with the densities given in the table?  Comment on your results.

Save your Word document (your name_lab1.doc) and attach it to an e-mail message to mbreinig@utk.edu.