A paddle wheel is used for stirring a liquid contained in a tank supplied 6000 kJ of work and during the stirring operation the tank lost 1500 kJ of heat to the surroundings. If the tank and liquid are considered as a system what will be its change in internal energy.
First law of thermodynamics tells that
\[dQ=du+dW\]
Therefore
\(-1500=du-6000
\\\Rightarrow du=6000-1500
\\\Rightarrow du=4500\;kJ\)
So change in internal energy of the system is 4500 kJ
