1. Conservation

Rate of Change Accumulation = In – Out + Generation – Consumption

\[ \frac{dA}{dt} = \dot{m}_{in} - \dot{m}_{out} + r_{gen} - r_{cons} \]

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Example 1: Water Draining from a Bucket

\[ \frac{dm}{dt} = \dot{m}_{in} - \dot{m}_{out} + r_{gen} - r_{cons} \]