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# Need help for a SL P.1 question

help SL paper question exam
2 replies to this topic

### #1 Linnsan Posted May 09, 2012 - 17:20

Linnsan
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• Exams: May 2012
I'm going through old paper 1 exams and stumbled upon the following question which I'd like some help solving. I'll show you what I have managed to do so far.

"A block of metal at a temperature of 90 C is placed in a beaker of water at a temperature of 0 C. The mass of the metal block and the mass of the water are equal. The final temperature of the water and the metal block is 9 C.
Which of the following is the best estimate of the ratio: specific heat of water/specific heat of metal?"

I thought the following. The heat lost by the metal= the heat gained by the water.

So: m * cmetal * (Tmin-Tmax) = m * cwater * (Tmax-Tmin)

Cancelling both masses since they're equal and putting in the temperatures gives:

cm * (9-90)= cw* (90-9)
cm * (-81)= cw* 81

That's where I got stuck. Have I done something wrong?

The alternatives are A: 1/10 B: 1/9 C: 9 10 and the correct answer is C: 9.

Please help, and thanks in advance

### #2 HiggsHunter Posted May 09, 2012 - 17:42

HiggsHunter
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Yes, you should have Cm * (90-9) = Cw * (9-0)
So Cw/Cm = 81/9 = 9 (Answer C)

### #3 Linnsan Posted May 09, 2012 - 17:48

Linnsan
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• Local time: 05:02 PM
• Exams: May 2012
Ahhhh thanks. It was the 0 that got lost into space