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Buoyancy: Helium-Balloon Critical-Thinking Answers for Linked Questions
 © Donald Reinhardt, March 7, 2013
Here following are the answers to the original questions posed at this link called:
Buoyancy: Helium-Balloon Critical-Thinking Questions with Linked Answers  
 
 
This experiment involves two balloons of the same mass (consider this as simple weight) filled with equal volumes of gas.

Questions and answers:

  1. Question: If both balloons are released at the same moment and allowed to rise, what would we expect to happen over the course of time?  Answer: This question did not define the gas, but we shall assume that the gas was a lighter than air gas in terms of density. Therefore, we can assume that since the volumes of the gas were equal as well as the mass of both balloons, then these balloons should have risen (accelerated) and reached the same final height as one another with all other factors and conditions being equal or constant.
  2. Question: Assume the same balloons as indicated above. One balloon was filled with helium gas, the other is filled hydrogen gas. Explain what happens when the balloons are released simultaneously. Answer: This is an interesting question because you would have to guess, if you did not know, that one gas is different from the other and the lightest gas (hydrogen in this case) would cause the balloon to be buoyed up and accelerate faster than the helium balloon. Because the volume and weight of the displaced air pushes upward at a greater force than the gas inside the balloon, we would also expect the hydrogen balloon would rise to a height greater than the more dense helium-filled balloon.
  3. Question: Assume that the ground air temperatures are equal when helium-filled balloons are released on a cloudy day and other totally-similar balloons are released at the same location on a bright, sunny day. What behavior or observations would you expect regarding these balloons as the balloons rise? Answer: If the balloons start out at the same temperature on the ground as they rise, the sunny-day released balloons of same volume and mass will tend to be warmed more on a sunny day then a cloudy day. The sun’s thermal energy would cause the volume of gas inside each balloon to expand and would cause each balloon to accelerate faster and ultimately reach a greater height than on a cloudy day with all other factors being equal.
  4. Question: It is a nice, bright and clear day and two identical helium balloons are released simultaneously. One balloon is pure white and the other intense black. What do you expect to happen over the course of the next hour and why? Answer: The white balloon will reflect light and tend not to absorb as much heat as the black balloon. Therefore, the black balloon will heat up, expand the balloon gas volume and create greater buoyancy. The black balloon will rise faster and higher than the white balloon.
  5. Question: When helium-filled balloons are released into the air indicate any and all conditions or circumstances that will cause these balloons to return back to earth. Answer: The balloons will return to earth as a result of many different actual and potential factors including:

·        Slow, natural escape of the helium gas from the sealed balloon

·        Escape of helium gas from the balloon as a result of any imperfect seals or closures at the fill port

·        Damage or puncturing of the balloon shell due to hail, flying debris, small minute particles of space or atmospheric dust or meteorites as some potential possibilities.

 

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