eli5: Why are refrigerator doors harder to open when they’ve just been closed?
In: Physics
Most fridge doors have a magnet behind the rubber seal that makes the door stick to the fridge when closed. This way the fridge stays properly sealed shut since you don’t want air to get out/in.
Each time you open the door you are forcing that magnet apart from the frame.
When the door is closed, the air inside cools. Air expands with heat and contracts when cooled.
The fridge door is not a perfect airtight seal. So the air pressure inside and outside will eventually equalize (as the air inside cools, warm air will slowly leak in and balance the pressure). So the first time you open the door, the inside and outside are at equal pressure (despite being different temperatures), and it’s easy to open the door.
When you open the door, all of the cold air “falls” out the bottom of the door (cool air being more dense, and therefore heavier, than warm air). This is replaced by warm air entering near the top of the door. When you close the door, you now have a mass of warm air in contact with the walls of the fridge and the items in the fridge. This causes a rapid cooling of the air, which makes it condense, which creates a vacuum inside the fridge. If you open it again soon enough, you must fight this negative pressure sucking the door closed.
If you wait long enough, the door seals will leak enough air in to allow the pressure to equalize, and it becomes easier to open again.
I think it has something to do with a vacuum upon initial closing and after a little bit of time, it equalizes making it easier to open…
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