IGCSE Pressure Question: How many balloons can be inflated?

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Homework Help Overview

The discussion revolves around a physics problem related to pressure and volume, specifically involving the inflation of balloons with helium from a cylinder. The original poster presents a scenario with given values for the volume and pressure of helium in the cylinder and in the balloons, seeking to determine how many balloons can be inflated.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply the ideal gas law concept by using the relationship between pressure and volume to calculate the number of balloons. Some participants question whether the helium cylinder would be completely empty after inflating the balloons, while others explore the implications of pressure differences.

Discussion Status

Participants are engaging in a back-and-forth regarding the assumptions made in the problem, particularly about the final state of the helium cylinder and the pressure dynamics involved. There is no explicit consensus reached, but some guidance is being offered regarding the interpretation of the problem.

Contextual Notes

There are references to analogies with electricity problems, which some participants challenge, indicating a potential misunderstanding of the physics principles at play. The age of the thread is also noted, suggesting that the discussion may have evolved over time.

UnknownGuy
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Hi, very quick question... It does like this: Helium in a cylinder (Which will be used to inflate a number of balloons) has a volume of (6*10-3) cubic meters and a pressure of (2.75*106)Pa. The pressure in each of the helium balloons is (1.1*105)Pa, and the volume of each balloon (3*10^-3) cubic meters.The temperature of helium does not change. How many balloons were inflated?

-How i solved it: Pressure * Volume = Constant so... (6.0*10^-3)*(2.75*10^6)=V2*1.1*10^5... V2= 0.15m3... Now what i did here was divide the total volume of helium at 1.1*105 by the volume of helium in each balloon and so...0.15/3*10-3... My answer was 50 balloons.

-Mark scheme has the following answer: (0.15-(6*10-3))/3*10-3... Can someone tell me where i went wrong?
Thanks in advance.
 
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Do you expect the helium cylinder to be completely empty after all the balloons that can be inflated are inflated?
 
gneill said:
Do you expect the helium cylinder to be completely empty after all the balloons that can be inflated are inflated?
If the volume of helium in the balloon is 0.15m3 at that pressure, then why not? We use all the 0.15m3 because 0.15 is divisible by 0.030 without any remainders...
 
UnknownGuy said:
If the volume of helium in the balloon is 0.15m3 at that pressure, then why not? We use all the 0.15m3 because 0.15 is divisible by 0.030 without any remainders...
So the final pressure in the cylinder will be zero? A perfect vacuum? How does the last of the gas get moved to balloons where the pressure will be nonzero?
 
gneill said:
So the final pressure in the cylinder will be zero? A perfect vacuum? How does the last of the gas get moved to balloons where the pressure will be nonzero?
Ah, now I understand.. Thank you very much!:biggrin:
 
:smile:
 
gneill said:
Do you expect the helium cylinder to be completely empty after all the balloons that can be inflated are inflated?
Yes just like in electricity questions we ignore resistance
 
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Pegasus said:
Yes just like in electricity questions we ignore resistance
Please note that this thread is more than 6 years old. Also note that in electricity questions we don't usually ignore resistance, especially when there is current flowing.
 
Pegasus said:
Yes just like in electricity questions we ignore resistance
Your analogy does not work. The balloon filling problem is more akin to charging capacitors from a given capacitor.
And the correct answer to @gneill's question is no. Or were you being sarcastic?
 

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