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The Buoyancy of Balloons

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Aleph Anguiano

on 17 June 2014

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Transcript of The Buoyancy of Balloons

The objective of this physics science fair project is to measure how the buoyancy of helium-filled latex balloons changes over time. Since the helium escapes out of the latex balloons .
•Metal spoons (3)
•Masking tape
•Permanent marker
•Scale, accurate to 1 gram (g) or less
•Latex balloons, filled with helium and ribbon attached so you can hold them (9); available at party supply stores and some grocery stores
•Lab notebook
•Graph paper

Balloon Buoyancy
Helium balloons float because the helium is lighter than the surrounding air. This means that the weight of the air displaced by the balloon is greater than the weight of the balloon and the gas inside, making the balloon float . Buoyancy is the force that exactly is the difference in the weight of the balloon and its contents (such as a ribbon), versus the weight of the volume of air displaced.
Helium balloons sink over time because they are made out of latex . Latex is a permeable membrane , which means that it has tiny holes that allows the helium atoms to escape over time . Helium escapes from latex balloons faster than air does because helium atoms are smaller . There is a point at which the buoyancy supplied by the helium equals the weight of the balloon and its contents and it floats in mid air, neither rising nor falling. This is called neutral buoyancy.

1.To start, label the three spoons using the masking tape and the permanent marker. Label them A, B, and C.

2.Weigh each spoon and record the values in your lab notebook.

3.Attach three balloons to each spoon.
a.Attach the balloons near the end of the ribbon, so that extra ribbon is not hanging from the spoon.
b.Trim any extra ribbon with the scissors, as needed.

4.Weigh each spoon with the balloons attached.
a.The balloons should be free to float above the scale.
b.Note the weights in your lab notebook for spoons A, B, and C.

5.Repeat step 4 every 8 hours, until the balloons have lost most of their buoyancy. a.8 hours is just a suggestion. Use your own judgment about how often to weigh the spoons.

6.Poke a hole in each balloon to let any remaining helium escape.

7.Weigh the balloons from the three sets by removing the spoons from the balloons and then weighing each balloon-and-ribbon set (a set is made up of three balloons and three ribbons). Record all data in your lab notebook.

The rate of buoyancy loss (lift decay) was linear over time, not at a non-constant rate .
The Buoyancy of Balloons
Weight of Spoons
How soon can the balloons in advance start deflating? In this science fair project, you will use a simple scale to measure the lift supplied by a set of balloons, and determine the rate of lift decay.
Does the balloon lose its buoyancy at a constant rate, or does the rate change over time? What is the rate of lift decay?

Equation :
Buoyancy =

weight of spoon − weight of spoon with balloons attached + weight of balloons and ribbon

Graph your data, with time on the x-axis and buoyancy on the y-axis.

Spoon A= 36.6g
Spoon B= 36.6g
Spoon C= 36.6g
Weight of Spoons + Balloons (Start)
Spoon A= 8.2g
Spoon B= 8.2g
Spoon c= 8.2g
If the balloon loses its buoyancy at a non-constant or linear rate , then the balloon will lose its buoyancy at a constant rate .
Spoon A= 18.4g
Spoon B= 18.4g
Spoon C= 18.5g
8 hours
16 hours
Spoon A= 33.1g
Spoon B= 33.1g
Spoon C= 33.1g
The Buoyancy
Spoon A= 37.5g
Spoon B= 37.5g
Spoon C= 37.5g
8 hours :
Spoon A=27.3
Spoon B=27.3
Spoon C=27.2
16 hours:
Spoon A=12.6
Spoon B=12.6
Spoon C=12.6
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