It seems like it's simple math but I'm not sure?

[lesdayy]

Homework Statement

A 300 g cup of coffee at 90°C is too hot to drink, so a person puts in a 30 g of cold water at 10ºC. What will the final temperature be? (Hint: you don't actually have to calculate, think about the range the temp would have to be in)

Relevant Equations

I dont believe there is one. I tried just simple math but it seems to good to be true

I don't believe there is one. I tried just simple math but it seems to good to be true.

 

[Gordianus]

There is a relevant equation. Can you name it?

 

[berkeman]

Which temperature scale should you use when calculating the new temperature?

Edit/Update -- As long as you are just calculating the *change* in temperature from mixing the two liquid samples, then I don't think it matters if you think about it in terms of Celsius or Kelvin. When finding the $\Delta T$ change in temperature the results should be the same.

 

[kuruman]

Start with the realization suggested by the hint: the final temperature cannot be greater than 90°C or less than 10°C. It has to be in-between, i.e. some kind of average. What kind of average? If I gave a test and 300 students got a score of 90 and 30 students got a score of 10, what would the average score be?

It's amazing how something familiar becomes unfamiliar when seen in a new context, isn't it?

 

[PeroK]

Homework Statement:: A 300 g cup of coffee at 90°C is too hot to drink, so a person puts in a 30 g of cold water at 10ºC. What will the final temperature be? (Hint: you don't actually have to calculate ...

I don't really agree with this. You need a physical understanding of what is temperature and some mathematics to support that model. The calculations may be easy once you have those things, but everything is linear!