Problem 1.

A rapidly spinning paddle wheel raises the temperature of 200mL of water from 21 degrees Celsius to 25 degrees. How much a) work is done and b) heat is transferred in this process?

Solution:

In this problem the work is done by the friction force. All the work will go to increase the internal energy of the water, which can be calculated as:

Where - specific heat of water, .

There are no heat transfer in the process.