Physics Question Related Pressure

[JamSmith]

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.

Edited March 14, 2017 by JamSmith

[DrP]

Think about it.... Up a mountain, is the air hotter? Or is it at a lower pressure?

 

also - what would happen if the air outside the packet was hotter? what would happen if it was at a lower pressure?

[JamSmith]

Think about it.... Up a mountain, is the air hotter? Or is it at a lower pressure?

 

also - what would happen if the air outside the packet was hotter? what would happen if it was at a lower pressure?

Maybe the potato chip bag was sealed at the surface pressure. And the pressure at the top of the mountain is less than surface pressure. So the packet's pressure is higher than the outside pressure and that is the reason why bag inflates like a balloon. I think I am doing right!

 

 

I am not sure about what you asked If the air outside hotter, I am just assuming that,

" If the air outside hotter then maybe the bag will slowly inflate like a balloon..!! Because the air has a certain amount of heat, which it carries with it as it rises". or The air inside expands until the pressure inside is the same as that outside.

Some weather balloons explode at height.

Edited March 15, 2017 by JamSmith

[DrP]

You are right about the pressure. It was sealed at ground level and the pressure was higher. Going to the mountain top reduces the air pressure outside of the bag and it will swell. I am pretty certain it doesn't get hotter as you go up a mountain - quite the opposite at high altitude. I don't think temperature has anything to do with it.

[Bender]

Temperature can play a role if you heat the air inside the sealed bag, which will also increase its pressure. The can be done regardless of outside temperature or pressure, so it is not really relevant to the original question.

[mistermack]

If the bag was sealed at sea level, it then contained a fixed volume of air, once it's sealed.

As you climb the mountain, the outside pressure drops, and so will the pressure in the bag, if it's not tightly packed.

With the drop in pressure inside the bag, the gas inside will expand. As you climb, the air inside the bag will keep expanding, as the pressure keeps dropping. Once the bag becomes tight, the tightness of the bag prevents the air inside the bag from expanding any more. So then you have a pressure difference between the inside and the outside of the bag, so the bag will become fully tight, like a balloon, and will keep the gas inside under higher pressure than the outside air.

 

The temperature outside will play a part. It will cool the gas in the bag, and work AGAINST it's expansion.

But if the bag expands, then the pressure effect has outweighed the cooling effect.

[JamSmith]

You are right about the pressure. ......

 

If the bag was sealed at sea level, it then contained a fixed...............

Thank you, both for the guidance.