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Abstract Balloons are a festive addition to many celebrations. You've probably noticed, though, that over a short period of time, helium-filled latex balloons start to lose their buoyancy. So when you're planning your next party, how soon can you buy the balloons in advance before they 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.Objective The objective of this physics science fair project is to measure how the buoyancy of helium-filled latex balloons changes over time. Introduction Helium-filled balloons float because the helium is lighter than the surrounding air. In other words, the weight of the air displaced by the balloon is greater than the weight of the balloon and the gas inside, so the balloon floats upward.
Latex is a permeable membrane, which means it has very small holes that allow the helium atoms to escape. Helium escapes from latex balloons faster than air does, because of the small size of helium atoms. As the helium trapped inside of a latex balloon slowly escapes, the balloon starts to sink. There is a point at which the buoyancy supplied by the helium just equals the weight of the balloon and its contents (and any attached ribbon), and the balloon hovers in mid air, neither rising nor falling. This is called neutral buoyancy. In this science fair project, you will use a simple scale and some balloons to investigate the following questions. Does the balloon lose its buoyancy at a constant rate, or does the rate change over time? What is the rate of lift decay? Terms, Concepts, and Questions to Start Background Research
Questions
Bibliography
Materials and Equipment
Experimental Procedure Performing the Experiment
Analyzing Your Data
Equation 1:
Variations
Credits David Whyte, PhD, Science Buddies
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