# Temperature of Iron.

1. Sep 16, 2004

### JayseR

For most of you experts out there, this should be fairly simple to answer. Well, technically, all it takes is logic to answer this:

A block of Iron has a temperature of 10 degrees celsius.
There is a second block of iron, identicle to the first, that is 2x the temperature of the first block of iron.

What is the temperature of the second block of iron?

2. Sep 16, 2004

### The Bob

40 degrees celsius.

3. Sep 16, 2004

### BobG

Using my Post 1491 analog calculator, I line up 10 degrees Celsius with the left index, move the cursor to 2 on the D scale, read 293 degrees Celsius on the Celsius scale. (select to see answer).

4. Sep 16, 2004

### Gokul43201

Staff Emeritus
BobG, surely, I have no idea what you're talking about. Maybe that's because I really haven't much used calculators, least of all, the analog ones you're so fond of. Somehow, you seem to have lucked out and gotten the right answer.

5. Sep 16, 2004

### recon

Wow...BobG, did you really need a calculator for that? Your reply almost put me off attempting the teaser.

If BobG's answer is correct (I think it is), then you really do need a knowledge of absolute temperatures and not just logic.

Twice 283 K (10 degrees Celsius) x 2 = 566 K = 293 degrees Celsius.

Highlight the empty space above to behold my answer. :tongue2:

6. Sep 16, 2004

### Clausius2

The question is incompleted. It depends of the dynamic state of the observer. If an observer is attached to a reference frame travelling a speed near light speed, then the measurements would be done by means of photoelectric instruments. The thermal energy will depend on the reference frame, and so the temperature.

Sounds pretty well, isn't it?

7. Sep 16, 2004

### JayseR

Technically, BobG is right. If you convert 10 degrees celsius into kalven, then double that number, and convert the doubled number back into celsius, you will get bob's answer. Good job :)

8. Sep 16, 2004

### The Bob

Which Bob and what is the answer???

9. Sep 16, 2004

### Gokul43201

Staff Emeritus
The correct answer is 293C. The absolute scate for temperature is the Kelvin scale. So to double the temperature, you must double the Kelvin temperature.

10. Sep 16, 2004

### The Bob

Understood. Cheers.

11. Sep 16, 2004

### JayseR

yuppo! that's right, and I'm prettty sure I said that BobG was right.

12. Sep 16, 2004

### The Bob

Sorry.

13. Sep 16, 2004

### ceptimus

How do we know that temperature is a linear scale? If it is a measure of the kinetic energy of the molecules that make up a substance, then that energy increases as the square of the average (for some meaning of average) molecular speed.

The Celcius scale is fixed at two points (0 and 100) by boiling and freezing pure water at a certain atmospheric pressure. but what shape is the line joining these points? Is it a straight line, or a parabola? In what sense is 50 degrees C 'half way' between 0C and 100C ?

14. Sep 16, 2004

### recon

I guess no one saw my solution in my previous post. I shouldn't write my answers in white next time. :tongue:

15. Sep 17, 2004

### BobG

I saw it.

But, the use of my 1955 calculator, which you made fun of me for using, which has never had a new set of batteries installed in it, which is just now finally beginning to get that nice broken in feel to it, and which should last at least another 25 years, enabled me to get my answer in first.

You gotta love good bamboo.

16. Sep 17, 2004

### Gokul43201

Staff Emeritus
Linear in what ? Temperature is not a linear function of the RMS velocity, but is linear in the average KE.

Is it a straight line, or a parabola? [/quote]

This question doesn't make sense unless you specify what you're plotting the temperature against.

This can be answered. The total kinetic energy of 2n molecules of a thing at 50C is the same as the total KE of n molecules at 0C and n at 100C.

17. Sep 17, 2004

### ceptimus

Thanks. I should have known that, but didn't.