Heat and Internal Energy

2007-10-16 6:38 am

PLEASE SHOW YOUR STEPS

Q.1 Water of mass 0.2kg at 20°C was added to water of mass 0.3kg at 75°C .

Calculate the temperature of the mixture.

Q.2 The heat capacity of a copper cup with a mass 0.5kg.

If 250kg of water at 5°C is added to the cup at 25°C , find the temperature of the water in the cup.

更新1:

sorry, I made the mistake : If 250g of water at 5°C is added to the cup at 25°C , find the temperature of the water in the cup.

回答 (2)

爛gag神

2007-10-16 7:18 am

✔ 最佳答案

1.
Let the final temperature of the mixture be T
0.2 x 4200 x (T-20)=0.3 x 4200 x (75-T)
840T - 16800 = 94500 - 1260T
2100T = 111300
T=53
Therefore, the final temperature of the mixture is 53 degree celcius

2.
Let the final temperature of the water be T
0.25 x 4200 x (T-5) = 0.5 x 370 x (25-T)
1050T-5250 = 4625-185T
1235T = 9875
T=8.00
Therefore, the final temperature of the mixture is 8.00 degree celcius

2007-10-17 00:16:08 補充：
I am not gd at Phy
and I am a F.4 boy only

參考: 自己

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Sheung Kan

2007-10-16 6:52 am

The calculation maybe (20℃+75℃)÷2.
=47.5℃

參考: calculating by myself.

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