Weight of air-filled balloon vs empty balloon

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SUMMARY

The discussion centers on the comparative weight of an air-filled balloon versus an empty balloon, both of equal mass. When weighed in air, the air-filled balloon experiences an upthrust due to its lower density, making it appear lighter. In a vacuum, however, the air-filled balloon's weight is greater than the displaced air, as the internal pressure is slightly higher than atmospheric pressure. The conclusion is that the air-filled balloon weighs more than the empty balloon when considering the effects of buoyancy and pressure differentials.

PREREQUISITES
  • Understanding of Archimedes' principle
  • Basic concepts of density and buoyancy
  • Knowledge of pressure differentials in gases
  • Familiarity with the behavior of gases in different environments (air vs. vacuum)
NEXT STEPS
  • Study Archimedes' principle in detail
  • Explore the concept of buoyancy in fluids
  • Learn about gas laws and pressure differentials
  • Investigate the effects of density on object behavior in various mediums
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Students studying physics, educators teaching buoyancy and density concepts, and anyone interested in the principles of fluid mechanics and gas behavior.

ritwik06
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Homework Statement


Take 2 rubber balloons A and B of equal mass. Balloon A is filled with air and balloon B is left empty and the two are weighed in a pan balance. What will you observe and why?




2. The attempt at a solution

The balloon with air will appear lighter if experiment is conducted in air and vice versa if in vacuum. Am I right?
 
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The question is asking which balloon is heavier its has nothing to do with the conditions of the experiment.
 
Kurdt said:
The question is asking which balloon is heavier its has nothing to do with the conditions of the experiment.

Then I think the one with air is heavier. What do you think? This was a 10 marks question. They won't take just a one line answer. What would you say?
 
ritwik06 said:

Homework Statement


Take 2 rubber balloons A and B of equal mass. Balloon A is filled with air and balloon B is left empty and the two are weighed in a pan balance. What will you observe and why?




2. The attempt at a solution

The balloon with air will appear lighter if experiment is conducted in air and vice versa if in vacuum. Am I right?
You are right about the second situation, but not about the first. What is the net force on each balloon?
 
Gokul43201 said:
You are right about the second situation, but not about the first. What is the net force on each balloon?

In the first case, that is in air, the balloon with air has less density, thus, an upthrust will act on the balloon due to air present. While in the second case, there will be no upthrust on the balloon filled with air.
 
ritwik06 said:
In the first case, that is in air, the balloon with air has less density, thus, an upthrust will act on the balloon due to air present.
How big is the upthrust? What about the weight? Isn't the weight also greater, due to the air in it? Does one of these two dominate? If yes, which one; if no, why not?

What does Archimedes say?
 
Gokul43201 said:
How big is the upthrust? What about the weight? Isn't the weight also greater, due to the air in it? Does one of these two dominate? If yes, which one; if no, why not?

What does Archimedes say?

I think the upthrust will be slight greater. Accordind to archimedes. Wt. of fluid displaced= upthrust.
 
ritwik06 said:
I think the upthrust will be slight greater. Accordind to archimedes. Wt. of fluid displaced= upthrust.
And why do you say the weight of the air displaced by the balloon is greater than the weight of the air in the balloon?
 
Gokul43201 said:
And why do you say the weight of the air displaced by the balloon is greater than the weight of the air in the balloon?

Oh! I am sorry they will be equal !:biggrin:
 
  • #10
Yes, to a resonable approximation, they will be equal.

But if you look at it carefully, the air inside the balloon actually weighs a tiny bit more than the air displaced by the balloon, because the air pressure inside the balloon is a little bit higher than atmospheric pressure.
 
  • #11
Thanks a lot :D
 

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