Physics Questions (Heat)

Scarbo

2009-08-15 2:01 am

1. Metal plates A and B are made of the same material. Plate A is at 10
℃ and plate B s at 50 ℃. The mass of plate A is 0.6 kg and that of
plate B is 1.5 kg. What is the temperature of the plates after they are
put in contact?

Answer:38.6 ℃

2. Mary is preparing a cupof instant noodles by adding 200g of water at
90 ℃ to 80g of noodles at 20 ℃. What will be the temperature of the
'mixture' just after mixing?
(Specific heat capacities ofwater and noodles are 4200 J kg-1 ℃-1
respectively.)
Answer: 78.8 ℃

How can I get the answer?
Thanks!!

更新1:

For question 2, Specific Heat Capacity of Noodles is 2000 J kg-1 ℃-1 .

回答 (3)

myisland8132

2009-08-15 9:09 pm

✔ 最佳答案

1 Let the final temperature is T
Heat gain = Heat loss
(0.6)(c)(T-10)=(1.5)(c)(50-T)
0.6T-6=75-1.5T
2.1T=81
T=38.6 ℃
2 Let the final temperature is T
Heat gain = Heat loss
(0.08)(2000)(T-20)=(0.2)(4200)(90-T)
160T-3200=75600-840T
T=78.8 ℃

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Scarbo

2009-08-15 3:15 am

Thx!!

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[匿名]

2009-08-15 2:10 am

For question 2, Specific Heat Capacity of Noodles is missing.

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