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Nairaland Forum / Science/Technology / Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? (2968 Views)
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Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by odijeks(m): 12:21am On Mar 13, 2016 |
This hot afternoon, I went to the freezer to take some water. I opened the door of the refrigerator, took out a bottle of chilled water and shut the door. I quickly poured out enough cold water into a glass cup and then tried to replace the bottle back in the fridge but the fridge door refused to budge. It was shut tight like as tho locked with a key and no matter how hard i pulled it was useless. Many of us have had such exp with our refrigerators at home and we all soon learnt that we have to wait for some time (say 30-40seconds) before the door opens with ease again. Now the question is, what is the principle behind this process? A good physicist here should be able to give a convincing explanation. |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by MathsChic(f): 12:49am On Mar 13, 2016 |
When the pressure between the inside of a container and its outside are pretty much same, you feel no resistance opening the lid or door to that container, as the case may be. When there is differential pressure between the inside and outside, then there is resistance. The direction of differential pressure will determine where resistance is coming from. Because the fridge is much colder than the outside, it is at a lower temperature. Remember the relationship between temperature and pressure? It's a direct relationship. If the temperature inside a container is really low, the gas particles in that container dont move rapidly, which means they are sluggish. That translates to lower pressure. Think about a cooking gas container; its gas particles are bouncing all about the container looking for an escape, which is why when you create an outlet, they immediately rush out. These gas particles are at a higher pressure. Anyways, I digress. Back to the explanation, the lower temperature inside the fridge means the gas (air) particles inside the fridge have created a lower pressure situation inside it, lower than the atmospheric pressure (which is the pressure at room temperature). Because there is now differential pressure, when you try to pull the fridge open, there is resistance. But why is the resistance against opening the fridge? Because matter in the classical world generally tends to move towards lower pressure. This is the same reason your gas particles in the cooking gas (which are at higher pressure) are seriously looking for a way to escape. So, your fridge door continues to resist your pull because the door is gravitating towards the lower pressure in the fridge. The small seal areas on the door lip make this pressure translate into greater force and that's why you often need to pull hard to open the door. 9 Likes 1 Share |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Danfuster(m): 1:02am On Mar 13, 2016 |
MathsChic: Wow... Bravo!!!. I'm stoked. I couldn't have done any better. You must be an Engineer, you're most definitely one of the rare ones. 1 Like |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Nobody: 1:23am On Mar 13, 2016 |
Synopsis from mathschic's analysis: immediately you open your fridge door, a chunk of warmer air(different from the Cold air from fridge) floods in. When you close it, that air contracts while it's mixing with the cold air. It makes a suction(absorption) for about 60-120secs 2 Likes |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by ismoh90: 2:45am On Mar 13, 2016 |
Guy na lite Ooo dey cos am... if d frdge is cold, u wil xperience dat.. It mins u r getin constant lite 4 ur area |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by ladygudhead(f): 3:54am On Mar 13, 2016 |
MathsChic: Good one mathschic,please are you a mathematician or a physicist? |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by MathsChic(f): 7:37am On Mar 13, 2016 |
Danfuster: ladygudhead:Lol. Thanks. I studied engineering. However, I'm not practicing as one. I'm squarely into finance these days. |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by ladygudhead(f): 9:06am On Mar 13, 2016 |
MathsChic: OK,nice. |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by odijeks(m): 9:23am On Mar 13, 2016 |
[quote author=MathsChic post=43721726]When the pressure between the inside of a container and its outside are pretty much same, you feel no resistance opening the lid or door to that container, as the case may be. When there is differential pressure between the inside and outside, then there is resistance. Because the fridge is much colder than the outside, it is at a lower temperature. Remember the relationship between temperature and pressure? It's a direct relationship. If the temperature inside a container is really low, the gas particles in that container dont move rapidly, which means they are sluggish. That translates to lower pressure. nice one MathsChic. The cooling of the warm air dat goes into d fridge results in drop in pressure as d air contracts. Really love d analysis. Where i'm nt perfectly clear is on d process dat occurs whil we wait for d door to open wit ease again. I believe the pressure in d fridge would hav to increase again for d ease of openin. Hw does dis pressure increas happen? |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by MathsChic(f): 9:55am On Mar 13, 2016 |
odijeksActually this is a very good point you have made. Immediately after shutting the fridge, it's more difficult to open, because of the rapid cooling of the air that just entered. After a while, it's easier because, as you rightly noted, the air expands. What causes the increase? Most fridges have a small outlet, some kind of pressure-relief mechanism, that lets out air and allows for the expansion. If this were not there, pressure will just build up infinitely inside the fridge. Don't you think? But some fridges are not just air-tight and overtime, air will seep in through the door and pressure will equalize. 2 Likes |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by odijeks(m): 10:07am On Mar 13, 2016 |
ismoh90: No be say light constant like that o, the fridge is kinda superb. E sabi maintain cool temp after small light |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by odijeks(m): 7:48pm On Mar 13, 2016 |
MathsChic: Thanks., you've done justice to this one |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Feraz(m): 12:06pm On Mar 14, 2016 |
You good! MathsChic: The quoted, one of my greatest fears! |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Abudu2000(m): 10:09pm On Mar 14, 2016 |
That 1st poster is disillusioned....btw it is sealed with a tube like seal to keep the gas in,use ur brain boy |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by phetty(m): 5:36pm On Mar 15, 2016 |
Abudu2000: MathsChic analysis is scientific, to reasonable extent, though. But my opinion is that the rubber-like sealant around the tip of the fridge body and its door is the cause of what the poster experienced. The pull force the poster exerted while trying to open the fridge door wasn't enough to against the friction existing between the two surfaces. 1 Like |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by MathsChic(f): 12:56am On Mar 16, 2016 |
phetty:Did you say friction? That, of course, is not correct. MathsChic: |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by odijeks(m): 9:12pm On Mar 17, 2016 |
phetty: the seal is related like MathsChic rightly pointed out but she explains that it serves in preventing exchange of pressure between the fridge compartment and the atmosphere, which adds up. i don't think it can be related to friction cos that would mean there is no friction when the fridge finally opens easily, which really doesn't make sense. |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Xenox(m): 8:51pm On Mar 19, 2016 |
MathsChic: Great explanation! Your explanation doesn't explain why the door opens some secs afterwards as stated in the problem. Because as long as the low temp regime exists inside the refrigerator, I expect atmospheric pressure to prevail over the door due to the low pressure inside the refrigerator. |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by Holdrested77: 1:55pm On Dec 06, 2021 |
Thanks for the help guys |
Re: Why Are Fridge Doors Hard To Open Immediately After They Are Shut Close? by tbambam: 4:03am On Dec 07, 2021 |
MathsChic: Are you around Ibadan? Can we go on a date, I suggest amala date with plenty meat.. I need to hear more from where this is coming. Kindly dm me on Twitter @otunbatbam to exchange contact.. |
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