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Homework Help: Physics Question Related to Pressure

  1. Mar 14, 2017 #1
    • Member advised to use the homework template for posts in the homework sections of PF.
    I am not tech savvy. But I like to solve quiz relates math and physics.

    I was solving such questions and come across this question.
    "On a cloudy day, a sealed packet of potato chips is taken to the top of a mountain. The packet is found to be blown up like a balloon."

    What is the reason behind it?

    I found two reasons as per my knowledge,
    1. The air outside the packet is hotter than the air inside the packet or
    2. The air outside is now at a lower pressure than the air inside the packet.

    Which one is the right reason? Please guide me in detail.
  2. jcsd
  3. Mar 14, 2017 #2
    Atmospheric pressure decreases with altitude. The potato chip bag was sealed at the surface of the earth, so the pressure in the bag is the surface pressure. The pressure at the top of the mountain is less than surface pressure. So the inside pressure is higher than the outside pressure, and the bag inflates like a balloon.
  4. Mar 14, 2017 #3


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    Why would that cause the packet to blow up?
  5. Mar 14, 2017 #4


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    The air inside expands until the pressure inside is the same as that outside.

    Some weather balloons explode at height.
  6. Mar 14, 2017 #5


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    Or until the bag becomes taut, thereby maintaining a pressure difference.
  7. Mar 14, 2017 #6


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    There used to be a nice little experiment shown in junior physics classes at my school .

    A large glass jar had two tubes through the stopper . The end of one tube inside the jar was fitted with a small uninflated balloon . When the other tube was connected to a low power vacuum pump the balloon slowly inflated .
  8. Mar 14, 2017 #7
    I was not sure about the concept,
    I have read that the air has a certain amount of heat, which it carries with it as it rises. So just assumed about this possiblity.
  9. Mar 14, 2017 #8
    Thanks for the guidence. This information helped me to find proper reasons of my question.
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