RACHEL has two bowls of soup at 90'C with the same heat capa

来源：学生作业帮编辑：作业帮分类：英语作业时间：2024/05/24 04:56:12

RACHEL has two bowls of soup at 90'C with the same heat capacity of 2000J'C-1.SHE pours one of them into a cup at an initial temperature of 25'C and leaves the other one on a table.the cup has a heat capacity of 200J'C-1.if the bowl of the soup on the table cools at average rate of 18W while the soup in the cup cools at an average rate of 3W,calculate their temperatures after 45 minutes.'
题目中2000j‘C-1 和 200J'C-1 中的-1，意思是负一次方。

先翻译：
2碗汤90度,热容2000J/度
一碗倒进25度的杯子中（杯子热容200J/度）
碗中的汤,以18W速度损失热量
杯中的汤,以3W的速度损失热量
求45分钟后,两份汤的温度
解题：
倒进杯子后的温度：
（2000×90+200×25）/(2000+200)=84.1度
杯子中的汤降温速度：
3/2000=0.0015度/秒
（此处要注意：题目的描述是杯中的汤损失热量的速度是3W
而不是,连杯子带汤,损失热量的速度3W,

所以分母是2000,而不是2200,不需要考虑杯子的热容）
45分钟降温多少：
0.0015*60*45=4.05度
所以杯子中的汤,最后的温度84.1-4.05=80.05度
下面算碗中的汤,降温的速度
18/2000=0.009度/秒
45分钟降温0.009×60×45=24.3度
所以碗中的汤最后温度90-24.3=65.7度

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