Posts by John Hayward

 

  • Energy in System Dynamics Models

    Kinetic Energy Energy, a familiar concept in Newtonian mechanics, is a valuable way of describing behaviour in system dynamics models. For example, consider a stock with a constant flow, figure 1: For a positive value of f, stock x increases […]

     

  • Force and Impact

    In mechanics, force produces acceleration in an object. The same concept can be used in system dynamics to describe how any time-varying signal can cause acceleration in a stock – a dynamic variable. That signal may be exogenous or come […]

     
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  • Balancing Loops: Growth and Decline

    Early on in a system dynamics (SD) course, it is usual for a learner to be introduced to two types of first-order balancing loops: one where the stock grows, and one where the stock declines. Death Process Take the decline […]

     

  • Reinforcing Loops and Growth

    I have often seen the following causal loop used in system dynamics presentations to explain a reinforcing loop: Figure 1: Causal Loop Diagram of Simple Birth Process The argument then runs: the more population, the more births, hence more in […]

     
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Loop Impact

 

Newtonian Framework

 

Soft Variables