Cold Definition and 381 Threads

Homework Statement Imagine you've been walking outside on an cold winter's day. When you arrive home at your studio apartment, you realize that you left a window open and your 5 {\rm m} \times 5 {\rm m} \times 3 {\rm m} room is only slightly warmer than the outside. You turn on your 1-kW space...

So, I know that freezing them makes them last longer, but I was just curious... why? I've also heard that freezing them makes them glow less bright, and heating makes them brighter. Since its a chemical reaction, that doesn't use or produce heat I don't see how it should matter. Then again, I...

Heat is the the vibration of molecules in a medium. If this is so, then how is space cold if it is a vacuum. I'm aware that space has very few particles but I don't understand how heat is emitted. I'm guessing that it might have to do with radiation.

So, I have a cold. I hate colds... Not only do I feel completely under the weather but I have E&M homework to do. The problem is, thanks to the cough syrup, I can't keep a coherent train of thought! I'm going to hand in crap for this assignment! The one problem I started I working out a...

Why does cold dark matter imply a bottom-up scenario of structure formation? and why does hot dark matter imply a top-down scenario of structure formation? is it simply because cold dark matter is slow moving (non-relativistic) and slow moving things are more likely to clump together to form...

If you suddenly put your hand into very hot water it feels cold (or atleast, it's hard to tell if it's hot or cold) for the first second. Why is this so? Thanks.

I had an idea once which I'd like to go into a little. It involves how a fan or propeller draws in air verses only providing thrust. The idea is/was to cut down on aerodynamic drag and resistance a propeller imposes once the craft is up to speed. By having a remote fan/propeller air intake...

hi i'm a high school student. is there any way to change the heat, directly to cold?

Hello everyone, I've been on Electrical Engineering for a little while but new to this aspect of science. I'm not sure of course but when sunlight travels through space, would it be the approximate temperature of its' surrounding area, pretty cool? And when it hits our oxygenated atmosphere...

How does cold air travel? Isn't it like me flashing darkness at your face? Because cold is the absence of heat as darkness is absence of light. It's like nothing traveling. I know it's confusing.:confused:

Why is it that air going at a high rate of speed always cold? For example, fans throws air at high speed and it's cold and when we, human blow air fast is always cold. WHY?

Hello everybody! i have a dodge neon 97 and i want to know how much pressure (PSI) receive the charge suction of the air conditioner compressor system? because i wan't to put the gas refrigerant recharge by myself

I will be writing my final exam tomorrow evening, and I am currently stuck on the following practice problem. It would be very nice if someone could help me out and I will remain eternally grateful for your help! 1) (Multiple Choice) Which of the following statement(s) about Cold Dark Matter...

http://www.springerlink.com/content/75p4572645025112/

Hey guys, I'm new to these forums so I'm hoping i have posted this question in the appropriate thread. Recently, i noticed the electric heater in my fish tank had a volume of water around it all times which was rising, it made sense to me that the water surrounding the heater would be rising...

Is it possible to have a cold virus in your back or affect your back. I recently had a very bad cold and now my lower back is killing me. My mom says you can have a cold in your back. Is this an old wives tale?

Help me design my "carputer" to work in the cold (advice on building a heater) Hello. You guys seem to be a knowledgeable bunch, so I thought maybe I'll post thing. My problem is that I custom built a computer to run in my car and I really need some help. I live in Calgary, Canada where in...

Can someone briefly explain the definition or the difference between a cold and hot transition of light? Hot transition involves a change in an atoms vibration and standing wave patterns from absorbtion of higher frequency, such as skin sunburn from long exposures to ultraviolet light or...

I don't pay my electricity bill so if I build a sterling engine going out into the -40 degree weather...

1. A woman informs her engineer husband that "hot water will freeze faster than cold water". He calls this statement nonsense. She answers by saying that she had actually timed the freezing process for ice trays in the home refrigerator and found that the hot water does indeed freeze faster. As...

Does anyone know of some easy to build cold fusion? I’m seeking to generate electricity

Currently where I live, we are experiencing very cold winters (average temperature during the day is about 35 degrees Fahrenheit). Last summer was also a surprise where the average temperature was about 105 degrees Fahrenheit. I know that the latter event might be a cause of Global warming...

It is common to see children when hurt while playing given ice packs to the injured area. Why is this coldness good? Does it numb the injured area so sensory signals less frequently reach the central nervous system? Also dry ice such as CO2 is able to 'burn' skin because of its very low...

Does warm water rise or fall in cold weather? I think it falls Does it have to do with convection??

I'm not a physics guy. I'm not even sure that that this is the right forum, but "solid state" sounded appropriate. Here is a link to a beer refrigerator that will chill beer to 22 F without freezing. http://biz.yahoo.com/prnews/061107/cgtu049.html?.v=73 My question is how this is possible...

Heyas. Recently my brother showed me a trick with a plastic bottle of very cold water. It was out of the freezer, pretty cold, but not frozen. He took the bottle and slammed it against the counter and the bottle froze up. I'm at a loss for explaining why this happens.. The only thing I can...

Electrons are accelerated through a potential V into a cloud of cold atomic hydrogen. A series of plates with aligned holes select a beam of scattered electrons moving perpendicular to the plates. Immediately beyond the final plate, the electrons enter a uniform magnetic field B perpendicular to...

VOTE - You're So Cold, You're So Cold! Another contest, and another collection of terrific pictures. Keep in mind before you cast your vote that the theme of this contest is to depict a picture that leaves you cold, that gives you the chills, etc. You should not vote for just a "pretty" or...

[SIZE="5"]You're So Cold, You're So Cold! A few weeks ago we had a photo contest to depict the epitome of summer. This time, we go the opposite direction. The photo contest this week requires a photo which (i) makes you feel cold, (ii) leaves you with a cold feeling, or (iii) gives you the...

The Mpemba effect is about the phenomena of hot water freezing faster than cold water. Does anyone know how to pronounce Mpemba?

I usually use an average number of 2 kPa friction loss for normal tap water in pipes. Does anyone know if this number changes significantly up or down for water which is around 80 degrees C instead of 5?

Well, read the paper today. Ken Lay died of a heart attack. This guy ruined so many peoples lives (mostly older people's life savings who lost it all), that I could care less about his death. The way I see it, he saved the people he screwed from loosing more of their money to house...

Direction of heat? "Hot to cold..." Please explain. During a college prep class last year, my physics teacher said something about the direction of heat. He asked a student, "Which direction does heat go? From hot to cold, or cold to hot?" I'm pretty sure that's what he asked. I wish I had...

is chicago state university better than washington ? Except Wahington, Chicago, what good schools near the border, cold in winter, cool in summer you can introduce? I also want to know why school fee in Canada is cheaper than US, what do shcools in US offer better compare to Canadas ? The...

Hello, Could someone tell me the difference between the infection of a virus (or bacteria...) and to catch a cold? Do we have the same symptoms? In case we catch a cold why do these symptoms occur?

I disagreed to the responce my teacher gave to this question "Why does a metal door knob feel colder that a wooden one on a cold day?" He said it was because the metal one has a lower specific heat, and the wooden one has a higher specific heat. He gave the example of tile and carpet on...

well, i stumbled across this link: http://jlnlabs.imars.com/cfr/index.htm it seems unbelievable that something is really happening in there... then i started looking around the net to see what other people think: http://en.wikipedia.org/wiki/Cold_fusion...

I was thinking to myself, why does cold air go to the bottom of the room and the hot air to the top? At first the answer looked simple, the cold air is "denser" than the hot air. But if you think about it, at the molecular level the only difference between hot air and cold air is that the...

can someone help please my friend has hepititis b and is feeling COLD throughout the body symptom his stomach hurts what is the illness?

Where does the feeling of cold come from? Is it from heat rushing past cells, when we step outside in the cold, that creates this feeling we signal as cold?

A friend of mine were discussing the cold weather and how everyone's getting sick. I was then trying to figure out why exactly people to tend to get sick when it gets cold? I'm sure there some very logical explanation, but I could not for the life of me think what it was. Everyone knows your...

When you're cold, your body naturally burns calories to keep you warm. So it makes sense to me that if people were to just stay out in the cold enough, that they could lose some weight. Also, it seems that you could probabally figure out a formula to determine exactly how much weight you'll lose...

I'm a physics major in Alaska, where it's not uncommon to have temperatures of -40. Are there any interesting experiments or designs that I can do in my freetime that are convenient because of the cold weather? I remember learning briefly about gradients being a source of power. If...

The british press are forcasting a record cold winter, and a major betting company have slashed the odds for this. what are they basing their predictions on ?

http://www.arxiv.org/abs/astro-ph/0508624 This paper offers a fairly natural explanation for the universality of dark matter halo profiles. In this model the mass accretion history has two distict phases, first a fast phase dominated by frequent mergers of smaller condensations of CDM...

How can "cold" radiation heat? I have enough experience with steam radiators and heat lamps to know that they don't radiate enough heat to warm their surroundings to the temperature of the radiator or lamp. How then can ground and water emit radiation with sufficient energy to warm the air to...

Hi, recently I found something out by playing around with candles. Basically I heated some candle wax until it was completely out of its solid state (at least through the first approximation of my eye.) Then I continued to heat the wax until the liquid wax ignited and started to burn. Usually...

Cold sore :( Does anyone know a good way to get rid of cold sores. I Have this one on my cheek and its so hard to eat!

I have a weird question here :biggrin:. What exactly causes common cold? I'm aware it is caused due to viruses but why do doctors prescribe anti-biotics for common cold which are supposed to fight bacterial infection? Do the following cause common cold: *Eating ice-creams *Wet hair *Hot...

Has anyone tried to buy over the counter cold or allergy medicine lately? A lot of states have just started enforcing a new law that restricts sales of most cold and allergy medicines. I just stopped on the way home to pick up a box of Actifed (the best thing in the world for allergies...