Alright Science/Physics Geeks

#1
volinbham

volinbham

VN GURU
Joined
Oct 21, 2004
Messages
70,468
Likes
64,506
#1
I've got a vaccuum mug for coffee. At the top it's tapered so the outside of the metal and inside of the metal are very close together.

When I put on the plastic lid, the lid is loose. Once the lid is on for a minute, it's quite tight.

If heat expands the metal but not the plastic shouldn't it be looser?

Signed - curious coffee drinker in Birmingham.
 
#4
#4
Does the lid fit over the outside of the mug or primarily along the inside with just a lip over the rim? Is this an actual design feature so that you keep a tight lid - or just something you noticed? Also, if you take the lid off once it is tight and put it back on - is it hard to get on again, or does it pull off fairly easily again? (I'm going to be really bad at trying to answering this...it's going to be funny.)
 
#5
#5
If the lid is plastic, the heat will expand the diameter of the metal (the inner diameter of the lid). Therefore, it will fit tighter.
 
#6
#6
Most of the lid fits inside the mug - there are some horizontal ridges on it. It also has a lip that lays across the top of the mug (the lid looks like a upside "L" from the side).

Not sure if it's a design feature or not. I've noticed that when it's not in use, the lid is relatively loose, easy to take off and easy to spin within the mug. Once I put it on with a hot liquid inside, it is very snug and difficult to spin.

I assumed that the heat would increase the circumference of the mug relative to the plastic lid but the opposite appears to be happening. Thought it might have something to do with the vaccuum?
 
#8
#8
When something tubular expands, both the inner and outer diameters expand equally. Does that help?
 
#9
#9
It's all in the vacccccuum. That thing is badass.
Posted via VolNation Mobile
 
#10
#10
volinbham said:
It would have to shrink the inner diameter of the mug to make it tighter.
Click to expand...

VOLatile said:
When something tubular expands, both the inner and outer diameters expand equally. Does that help?
Click to expand...

I thought that it got tighter as it cooled from your original explanation, but after reading your more detailed description it is clearer now. Because it gets tighter as the metal heats up (from exposure to the coffee)...then VOLatile's (and Rasputin's) answer would seem right to me. The inner diameter does shrink as the inside metal pushes further inside and the outside metal pushes further outside (making the vacuum space a bit larger).
 
Last edited:
#11
#11
TennTradition said:
I thought that it got tighter as it cooled from your original explanation, but after reading your more detailed description it is clearer now. Because it gets tighter as the metal heats up (from exposure to the coffee)...then VOLatile's (and Rasputin's) answer would seem right to me. The inner diameter does shrink as the inside metal pushes further inside and the outside metal pushes further outside (making the vacuum space a bit larger).
Click to expand...

Or, if the coffee is hot to begin with and you immediately place a lid on it, inside the cup, you would have heated air between the surface of the coffee and the lid. Heated air is at high pressure. As the coffee cools, the air cools, which will lower the pressure inside the cup. If the pressure inside the cup falls below atmospheric pressure, then the atmosphere will "seal" the lid or make it seem as though the lid is tighter.
 
#14
#14
Rasputin_Vol said:
Or, if the coffee is hot to begin with and you immediately place a lid on it, inside the cup, you would have heated air between the surface of the coffee and the lid. Heated air is at high pressure. As the coffee cools, the air cools, which will lower the pressure inside the cup. If the pressure inside the cup falls below atmospheric pressure, then the atmosphere will "seal" the lid or make it seem as though the lid is tighter.
Click to expand...

It does feel as if it's a tighter to the side feel as opposed to a sucked on feeling.
 
#15
#15
If the pressure inside the cup is greater than or equal to the pressure of the outside atmosphere, then I could see it feeling loose. Seems as though there may also be some vacuum action working along with this. If the air gap between the surface of the coffee in the cup and the lid drops in tempurature, you would also get a drop in pressure, which would form a slight vacuum.

I think... :crazy:
 
#17
#17
volinbham said:
I've got a vaccuum mug for coffee. At the top it's tapered so the outside of the metal and inside of the metal are very close together.

When I put on the plastic lid, the lid is loose. Once the lid is on for a minute, it's quite tight.

If heat expands the metal but not the plastic shouldn't it be looser?

Signed - curious coffee drinker in Birmingham.
Click to expand...


If the coffee has been introduced into the container
Before the lid was put on the material expansion would
have already taken place,so it's probably the vacuum.
 
#18
#18
It's an effective lid since it works this way but I haven't figured it out.

I was thinking like getting a tight jar lid off. I assumed hot water over the lid expanded the metal but not the glass so the jar lid expands slightly (circumference gets bigger) relative to the glass jar and voila.

So, I'm a bit confused how expanding metal can create a smaller circumference.
 
#21
#21
orangeblooded2 said:
If the coffee has been introduced into the container
Before the lid was put on the material expansion would
have already taken place,so it's probably the vacuum.
Click to expand...

I was kinda wondering along those lines - if somehow a change in pressure within the vaccuum section actually pushes the inner metal inward.
 
#24
#24
Since this is the science thread:

I put a coke can in the freezer and it got bigger. I thought things got smaller in the cold. What's the deal?
 
#25
#25
allvol123 said:
Since this is the science thread:

I put a coke can in the freezer and it got bigger. I thought things got smaller in the cold. What's the deal?
Click to expand...

I suggest crawling in the freezer next time and taking notes on what happens...
 
New Posts
You must log in or register to reply here.

Advertisement



Back
Top