# A physics brain teaser!

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If today is zero degrees and tomorrow is going to be twice as cold, what temperature is tomorrow going to be?

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Mark Knowlesposted 15 years agoin reply to this

Twice as cold as what?

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Twice as cold as Zero degrees

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BDazzlerposted 15 years agoin reply to this

Assume 100 degrees is twice as hot as 50 degrees
Assume 25 degrees is half as hot as 50 degrees and is therefore 25 degrees is twice as cold as 50.
Assume Zero C in question ...
Covert to F temp now  =  32
Half of 32 is 16
Covert 16 F to C and we have -8.9 degrees C

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countrywomenposted 15 years agoin reply to this

BDazzler- You dazzle with your intelligence

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BDazzlerposted 15 years agoin reply to this

You are quite kind, and I don't think I congratulated you on your marriage!

Congratultions!

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AEvansposted 15 years agoin reply to this

Yes BDazzler Congrats again!!!!! hehehehe

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sandra rinckposted 15 years agoin reply to this

Ah but C doesn't have a zero degree and neither does F, so even if you did convert the temperatures all have but skipped Zero assuming that zero degrees is hot or cold.  But I really like how you put this, I am just not sold yet.

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BDazzlerposted 15 years agoin reply to this

Weellll ... I have a degree in Science and Math with a secondary emprasis on Chemistry.  This is the first I've heard about neither celcius or farenhiet having a zero ... I think you may be mistaken on this one Sandy.  Celcius is defined as the scale between the freezing point of water and the boiling point of water ... being between zero and 100 inclusive.

There is an error in this calculation, (well not an error, there's an implied assumption that is incorrect ) I'm just waiting for somone else to find it and point it out ... but the non-existance of zero isn't it.

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diplessposted 15 years agoin reply to this

One of the problems with this analysis of the problem is if you keep halving starting at 100 then you will never actually reach 0 i.e. 100 goes to 50 to 25 to 12.5 to 6.75 to 3.375 to etc all the way to infinity but you would still never reach 0 degrees so you can't use this method.

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packerpackposted 15 years agoin reply to this

There is nothing called cold in the world of physics. We measure heat and not cold. Temperature in any scale gives us the indication of presence of amount of heat energy and not cold energy as there is nothing called cold energy. Cold in just the absence of heat. Since we cannot measure cold so the question itself becomes invalid!

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Béla Mongyiposted 15 years agoin reply to this

Error: unspecified referential index

How can your robotic brain come up with such a question?

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Mishaposted 15 years ago

As an ipod in a glass of juice

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Lol, just realised that I still kept the title of the request I was answering. Hehe thanks for that, I've changed it now :-)

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nicompposted 15 years agoin reply to this

Well done.

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Paragliderposted 15 years ago

Meaningless question. What scale are we using? Farenheit, Celsius or Kelvin?

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Mark Knowlesposted 15 years agoin reply to this

But - even if we use a scale, it doesn't mean anything. "Cold" is a relative term

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Celsius my friend.

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Paragliderposted 15 years agoin reply to this

OK. Twice as cold can be taken to mean the same as half as hot, which is reasonable because temperature is a measure of hotness (not of heat which is measured in joules).

So first convert to Kelvin, so that you are working on an absolute scale. Then divide by two (which works because the scale is linear) and convert back to Celsius if you want to.

But temperatures of 136.5K (or -136.5C) are not survivable and so, subjectively are far colder than 'twice as cold'. In fact, though the temperature scale is linear, the human response to it is highly non-linear (rather like our response to loudness).

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BDazzlerposted 15 years agoin reply to this

Para's resposne is more correct than mine .... my response had one major problem ... a "Degree" in C is "Bigger" than a Degree in F and my response failed to take that into consideration.

Since a Degree K is the same size as a Degree C, Para has come up with the right answer.

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sandra rinckposted 15 years agoin reply to this

Well obviously I don't get it but in my mind, 0 and -0 are the same degree because this degree in terms of heat is undefined but hotter than whatever hot is, and likewise the same degree is absolute terms of cold is colder than whatever cold is.

So in one lump sum you could say that the hotter it is, the colder it is.  In stupid Sandy terms, it's like putting your hand it really hot water, it friggin burns it stings, just the same as putting your hand in really cold water, it friggin burns and stings.  Now put your hand in water that is twice as hot as whatever really hot it and it's likey you wouldn't feel a thing, same with cold.

Or dry ice is so cold it is hot or so hot it is cold.  Still not sold and and still view the the scales as irrelevant. 0x0=0 and -0x0=0 and -0x0=0 so -0[0] and 0[-0]  and 0/0=0 and -0/0=0 etc.. all = 0.

so just by the word problem alone 2x0 still = 0. and -2x0 still = 0...

but please keep trying to convince me.

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Mishaposted 15 years agoin reply to this

I'm with you here My Goddess

Never thought of changing the scale in the midst of calculations to be a valid method, and frankly really am surprised the guys seemed to take this idiotic challenge seriously

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sandra rinckposted 15 years agoin reply to this

me too, I guess that is why it was called a physics brain teaser.   after all, I am not a physicist.    doh!

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BDazzlerposted 15 years agoin reply to this

Seriously? Of coruse not, that's why I posted my erroneous answer first.... it's just that some of us find our fun differently than others:

Sandy your argument is valid for the Kelvin scale, in which zero truly is zero.  On the celsius scale, zero is defined as the freezing point of water.  So it's not absolute zero, it's jut an arbitrary number that someone called zero.

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Make Moneyposted 15 years agoin reply to this

Which direction is the wind blowing?  Just joking.

I would have said 0 too.

0x2=0

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knolyourselfposted 15 years ago

Actually there are a number of answers on Google. This has been one of them:
"That would depend on what temperature scale you are using. The scale which places zero degrees at the absolutely coldest point is called Kelvin. It has the same degree divisions as Celsius does. "Absolute zero," or zero degrees Kelvin, is the coldest temperature possible. This is the temperature at which all molecules stop all movement.
So, if you are measuring in Kelvin, twice as cold is not possible. (0/2=0) However, if you are using the Celsius scale, zero degrees is actually 273.15 degrees above absolute zero. So, twice as cold would be -136.575 degrees Celsius. Similarly, absolute zero in Fahrenheit is -459.67. Thus, from zero degrees F, twice as cold would be -229.835 degrees F."

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sandra rinckposted 15 years agoin reply to this

Still the answer would be zero degrees.  But I think this information is wrong.  1 degree Celsius is 32 degrees Fahrenheit so neither scale address absolute zero temperature.

Kelvin represents absolute zero temperate, and temperature address "heat or energy", really it is neither hot or cold.  Like Mark said, cold is a relative term.

So it would still be the same 0[-0].

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greathubposted 15 years ago

It depends on relative humidity too.

Moreover what is hot for you may be cold for me.

e.g. 21 degree celsius is hot for canadians and the same temperature is cold for people living in warm climates.

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diplessposted 15 years ago

Temprature is a measure of energy in a system and you can use different equations and laws to calculate the temprature in a system depending upon what you are measuring. For example you could use the 2nd law of thermodynamics and relate the temprature to the entropy of the system. Or we could use the zeroth law of thermodynamics, but the we need an idealized situation. The problem is that this question is too openended and therefore not a valid question, hence the problems in answering so there really is no VALID answer.

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diplessposted 15 years ago

Error: unspecified referential index

How can your robotic brain come up with such a question?

LOL

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Patty Inglish, MSposted 15 years ago

Among other things, it's a question sometimes asked in employment interviews to examine problem-solving skills -- Does the candidate 1) choose a scale and explain why (s)he chose it and offer an answer, 2) give an explantion that there is no reference point, or 3) give up and say "I dunno"? -- Or does he/she do something else, like call the Physics Dept of the local University from the HR guy's phone and relay the answer?

And, these questions can frustrate job candidates, espeically in a recession or after a layoff when a person may be worried about how to feed his/her children.

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ocbillposted 15 years ago

Uh yeah, like I will believe the TV weather forecaster. LOL.
Although, I like the -8.9 C answer though Alex Trebek

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Hawkesdreamposted 15 years ago

Who cares anyway, any temperature that is at 0 or below is gonna be bloody cold. Get out your woolley jumpers, hat gloves and scarfs and furry boots. Your temperature will be comfortable enough.

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B.Z. Alixandreposted 15 years ago

My problem with the question is along the lines already stated that cold is not a "real" science term.  If you conclude that temperature is a measure of energy in regards to how fast particles are moving then my answer would relate to half as cold being the point in which the molecules are moving half as fast.  But the progressions of speed in particles is not linear and not equal to other particles.  Ie: for water approaching 100 C (but not yet arrived at) it takes more energy to obtain 100 C because it becomes steam at 100 C.  Imagine your pot of boiling water.  The part hovering over the pot as steam is 100 C but the part in the water is 99.9 C (or close to)  It takes time at the point of transformation from one state or another.  Alcohol has a much lower boiling and freezing point, therefor the particles are moving at different speeds as water at the same temperature.  Therefor half as cold as 0 C will be different for alcohol than for water.

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