Physics discussion

tonksy

tonksy

New Member
Okay so I present this issue as a discussion in physics. Initially the answer seems simple yet when I think on it more it doesn't.

My little suction cup magnifying mirror. It is suctioned cups to my bathroom mirror. Every 2 weeks or so it falls off into the sink. ALWAYS in the middle of the night. Winter, spring, summer, and fall. It is near the temperature exchange so it is constantly in a climate regulated area. It is not in direct sight of a window. The nearest windows to it are shuttered so warming sunlight and then lack of it shouldn't be a factor. Being that it's in the middle of the night there is no added humidity or moisture from a bath or shower. The cats don't get up on my sink area.
What gives? Why always in the middle of the night?
 
Because that's how long it takes for air to leak back behind the cup. You always put it back on at the same time each week, right?
 
Nope. I don't have a 9 to 5 so I shower when I feel like it. Sometimes I'll fix it immediately (it wakes me) sometimes I do it early in the morning if I am headed to the school (6-ish) and times like today when I'll do it when I decide to get dressed (probably soon as I need to vote).
 
Barometric pressure. When the pressure outside becomes lower than the artificial pressure created by the suction inside the cup, the suction fails and the cup falls.

Barometric pressure drops at night...and you can't control your house's pressure because your house is not air-tight.
 
That makes good sense...but what about sudden storms during the day? we get those frequently and the mirror never falls then.
 
Combination of factors. Humidity, Prof's leakage, Bish's barometric pressure, temperature changes, vibrations, probably a few other factors I haven't thought of. All of these factors just happen come together at night (no direct or indirect sunlight a contributing factor?) to create the proper circumstances. Does it happen at specifically the same time each time?
 
It's more a matter of 'the straw that broke the camels' back" - daily (nightly) variations of the pressure outside degrade the suction slowly...not enough to knock it down in one blow, but over a period of time..in your case, about every two weeks. The day it falls is the day that the suction reached it's breaking point. If you were to push on the cup once a week or so, it would probably stay up there forever.

There are other things like air-leaks (glass isn't perfectly smooth and neither is the cup) that'll affect the seal..but it doesn't sound like the primary cause. It'd fall more often in that case.
 
in re: the time. Not always the same time but always after midnight and before sunrise.
 
tonksy said:
in re: the time. Not always the same time but always after midnight and before sunrise.
Click to expand...

So even though it's always late at night, it's kind of random. I think Bish has the solution though, just push it down every so often.

High tech solutions is us'ns! ;)
 
Well, maybe we could use the Large Hadron Collider to generate a miniature black hole that would hold it up permanently if it didn't destroy the universe.

Just as a possible alternative.
 
Actually, I think you have suction-cup faeries ... they are notorious for middle-of-the-night shinnanigans. (Did I spell that right?)
 
My friend says that they're going to turn it on this Friday.

Hopefully the world does not end on 08/08/08
 
No one should be forced to watch the Olympics- it's against the Geneva Convention.
 
Lick the suction cups (or lick your funger and draw a circle on the edges of the cups, or otherwise get them wet) before you stick them to the mirror next time.
 
nalani said:
Actually, I think you have suction-cup faeries ... they are notorious for middle-of-the-night shinnanigans. (Did I spell that right?)
Click to expand...

shenanigans

I just love when someone actually asks me to be pedantic. ;)

One might note that it starts with "she." Indicative, don't you think?
 
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