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June 13th, 2011, 03:11 AM   #1
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Thermal Equilibrium

I need someone to show me steps in solving this...(should not be too hard for post graduate)
*note : my syllabus only reach thermal equilibrium in 2 objects only (just my interest to know how)

Given there are 3 beakers labeled A,B,C containing water with different mass and different temperature

where beaker A : 500g of water with 30C
beaker B : 300g of water with 50C
beaker C : 200g of water with 20C

and specific heat capacity of water i found in my textbook is 4200.

What is the temperature when all water from three beakers above is pour into one beaker? ( assume no heat loss to surroundings )
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June 13th, 2011, 03:52 AM   #2
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Re: Thermal Equilibrium

Neglecting the heat generated by turbulence and viscosity by the "pouring in" of water with kinetic energy you can assume that the " heat content" of the water (above that at 20 deg C) is
Mass of water times temperature - 20
In other words you are assuming specific heat does NOT vary with temperature.
So add up the "heat content" total
and the total mass
and use your common sense.
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June 13th, 2011, 02:10 PM   #3
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Re: Thermal Equilibrium

So you mean like this?

500g+300g+200g = 1kg
0.5kg(4200)(30) + 0.3kg(4200)(50) + 0.2kg(4200)(16800) = 142800

So....what is water temperature in C ?
When i assume no heat loss to surroundings i just means the heat equalize out among water.

Gin , mind show me a little steps ?

Sorry for being lack of physics sense , i like how physics turn around in calculations but i myself not really master physics.
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June 15th, 2011, 06:55 AM   #4
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Re: Thermal Equilibrium

Quote:
Originally Posted by rnck
So you mean like this?

500g+300g+200g = 1kg
0.5kg(4200)(30) + 0.3kg(4200)(50) + 0.2kg(4200)(16800) = 142800

So....what is water temperature in C ?
When i assume no heat loss to surroundings i just means the heat equalize out among water.

Gin , mind show me a little steps ?

Sorry for being lack of physics sense , i like how physics turn around in calculations but i myself not really master physics.
"Heat" = 500g times 30 gram.degrees + 300 times 50 gram.degrees + 200 times 20 gram.degrees
divide by total grams=1000 g, so temp above 0 C is 15 +15 + 4
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