Name:_______________________________Date:_______________Time:____________

Partner(s) Name:______________________________

ARCHIMEDES' PRINCIPLE (Please read section 15-7 (pages 329--332) of your text.

Purpose: To verify Archimedes' principle and to use it to determine the density of 

a) heavy solids     b) a light solid      c) a liquid

Apparatus: Electronic balance with weigh below hook, wooden block, Al block, lead sinker, hydrometer, copper sulfate solution, beaker(250 ml), graduated cylinder, small ruler or vernier caliper, and wiper paper.

Theory:

Archimedes's principle - The buoyant force acting on a partially or fully submerged object in a fluid is equal to the weight of the fluid it displaces.

unit of density = gram/cm³ ; cm³ = ml.

Density of water = 1 gram/ml = 1000 kg/m³.

Procedure:

1) Set up the ring stand about a foot above the lab-table. 

2) Attach the weigh-below-hook to the underside of the electronic balance and place it on the O-ring, and tare the scale.

3) Hang the aluminum block from the hook and measure its mass, which is the mass in air.

4) Place the lab-jack under the hanging aluminum block and put the beaker with water on it.

5) Slowly raise the lab-jack and submerge the aluminum block in water, completely. 

6) Observe the reading of the electronic balance, as you submerge the block, and describe it below. Also explain what you observe.

7) The scale reading when the block is fully submerged is the mass in water. Record this in the data table below.

8) Remove the aluminum block from the hook and put the beaker with water on the electronic balance.

9) Tare the scale.

10) Hold the aluminum block above the beaker and slowly lower it and submerge it in water, while holding it.

11) The scale reading will give the mass of the displaced water. Record this in the data table below.

12) Repeat the above measurements for a steel weight and a lead sinker.

Buoyant force in grams = Mass in air - Mass in water.

To find the volume of the metal block use Archimedes' principle and the fact that the density of water is 1 gram/cm³.

Density of a light solid (wooden block)

1) Find the mass of the wooden block using the electronic balance. Find the dimensions of the wooden block and calculate the volume of the wooden block. Use the mass and volume to calculate the density of the wooden block.

Mass = _________    Length = ____________    Width = ____________    Height = ___________

Volume = __________    Density = ________________ 

2) Now you will find the volume of the wooden block using Archimedes' principle. Tie the wooden block to the lead-sinker and find the buoyant force when both are in water.

3) Find the buoyant force when the lead-sinker is in water while the wooden-block is in the air.

4) Data from 2) and 3) above can be used to find the volume of the wooden-block.

    Buoyant force when both are submerged in water = ____________

    Buoyant force when the lead-sinker is in water     = ____________

    Volume of the wooden block                               = ____________

    % Difference for volume (between  1) and 4) above) = ___________

Density of a liquid

1) Use a hydrometer and measure the density of water and CuSo₄ solution.

    Density of water = ____________    Density of CuSo₄ solution = ______________

2) Use the lead-sinker and find the buoyant force in water and in CuSo₄ solution.

3) Determine the density of CuSo₄ solution.

Buoyant force in water                 = ____________ 

Buoyant force in CuSo₄ solution   = ____________

    Use Archimedes' principle and deduce:

    Mass of displaced water = ____________

    Volume of displaced water = ___________

    Volume of displaced CuSo₄ solution = ___________

    Mass of displaced CuSo₄ solution    = ___________

    Density of CuSo₄ solution               = ___________

    % Difference for density of CuSo₄ solution (between 1) and 3)) = ____________ 

Virtual Lab:

1. Visit the floating log web site.

    Use length of log =1m  and radius of log =0.5m.( Instead of the L=10 m and R = 2m  suggested by the website designers). You need only to change the mass added and the mass of the log before so the log just sinks.

2. Determine the mass it will support just before it sinks.______________________

3. Calculate the above mass using Archimedes' principle.______________________

Conclusion: