Sunday, August 2, 2009

A 200g aluminum cup contains 800g of water in thermal equilibrium at 80 degrees C. The combination of the cup?

and water is cooled uniformly so that the temperature decreases 1.5 degeers C per minutes. At what rate is heat energy being removed? Express answers in watts.








answer is 88 W but why?





specific heat of aluminum 900 J/Kg * C





specific hear of aluminum 4186 J/Kg *C

A 200g aluminum cup contains 800g of water in thermal equilibrium at 80 degrees C. The combination of the cup?
Heat lost by cup to drop 1 Deg. C= (mass1*sph1)=0.2kg X 900 J/kg


=180J/min


Heat lost by water to drop 1 Deg. C=(mass2*sph2)=0.8 X 4186 J/kg


=3348 J/min


Total heat loss per minute = 180+3348=3528 J/min


Heat lost to decrease 1.5 degrees C= 3528 X 1.5=5292 J/min


1 Watt= 1J/sec


Total watts= 5292/60


=88.2 W
Reply:(mass1*sph1+mass2*sph2)*1.5ºC/min





comes out to 88.2W

wedding florist

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