Chapter 2. Stocks and Flows -- 4 Exercises
(or return to the Guide to Exercises)

1. What Are the Units?

The variable A is measured in calories. Time is measured in seconds. What are the units for B? for C? for G?

2. Acceptable Units

Possible values for T are shown below. Only one of the values makes sense for the flow diagram in the previous exercise. Which value makes sense? 1) T = 0.25 calories/hour 2) T = 25 degrees Celsius 3) T = 2.5 hours 4) T = 0.25 per second

Which of the following is the only equation to make sense for E in the previous diagram? 1) E = 25 calories 2) E = 25 seconds 3) E = 0.25 (dimensionless) 4) E = 2.5 calories per square meter

3. Identifying Stocks & Flows in a Financial System
Click here to see a diagram of the cash flow of an Investor Owned Utility (IOU). The diagram is large, so be patient while it loads.

You'll see sources of funds on the left, uses of funds on the right. Sources and uses are expressed in millions of dollars per year. The assets and liabilities are expressed in millions of dollars. They will appear at the bottom of the diagram. Chapter 23 explains how system dynamics has been used to study the financial problems of IOUs. You may not have looked at chapter 23, but you should be able to identify the key stocks and flows based in the diagram.

What are the stocks?

What are the flows?

4. Flow Diagram for a Financial Model

Draw a flow diagram of a model to simulate the financial situation of an IOU (based on the large diagram). You probably don't know enough to include the converters and the information links, so limit your diagram to the stocks and flows.