Buoyancy and the Archimedes Force

Purpose: To investigate the force exerted by a fluid on a submerged object.


  • To learn how to measure the buoyancy force on a submerged object.


  • Graduated cylinders
  • A metal object
  • Mass Scale


When an object is submerged in a fluid it displaces fluid volume equal to its own volume.

The force exerted by the fluid on a submerged object is equal to the weight of the displaced fluid and is called the Archimedes force.

    (Buoyancy Force) =  (fluid density)  ×(the gravitational acceleration)  ×  (Displaced Volume)

Experiment, Data and Results

We will calculate the buyoancy force in two different ways and compare the value

Activity 1: Determine the buoyancy force by measuring the displaced volume

  • Fill the graduated cyllinder with water and mark the water level.
  • Submerge the metal object and mark the new water level.
  • Determine the displaced volume and calculate the buoyancy force.
  Initial water level     Final water level     Displaced volume     Buoyancy Force  

Activity 2: Determine the buoyancy force by measuring the mass and the apparent mass

Measure the mass of the object.

Submerge the object in water and measure its mass>

Calculate the boyancy force.

  True Mass     Apparent Mass     Buoyancy Force  
  • Questions.

    Do the two values for the buoyancy force agree?

    Which method do you think is more accurate. Justify your arguments.