On a flight to Europe, you notice that the packages of peanuts are puffed up. Why?
1. The peanuts have greater velocities at high altitudes, thus causing the peanuts to exert more force on the packaging.
2. The jet is over-pressurized at high altitudes, thus causing the gas inside the packages to expand.
3. The air in the jet is approximately ten times hotter than on the ground, thus increasing the temperature of the gas in the packages.
4. The packages are puffed up on the ground due to overinflation with helium. This type of packaging provides extra buoyancy for aircrafts.
5. They were packaged at a higher pressure on the ground, thus causing the gas inside the packages to expand in the sky where the jet is at a lower pressure.