Buoyancy and the Archimedes Force

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

Objectives

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

Equipment

• Graduated cylinders
• A metal object
• Mass Scale

Theory

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.