Introduction

A model is any set of ideas that can help you explain why certain phenomena occur as they do. In the two units of Module MSE, you may have used models that explained magnetic and static electric phenomena by imagining how certain magnetic and charged entities might be arranged (and rearranged) in materials. In those units we spend most of the time developing the models themselves and only try to write formal explanations once the class consensus models had been established.

In this unit, however, the basic assumptions of the energy-based model have already been established and so we can begin to write formal explanations using these, just applying the same ideas to different situations as they are introduced.

Structure of and Explanation

While they may seem very different to the models developed in Module MSE, the ideas about energy transfer and energy changes during interactions introduced in the previous activity are also a model because they rely on certain basic assumptions and then use these to explain many different phenomena.

  The basic assumptions of the energy model are:

• Certain observable properties of an object can be associated with different types of energy. (For example, speed is associated with kinetic energy.)
• From any change in an observable property we can infer a change in the corresponding type of energy. (For example, when the speed of an object changes, so does its kinetic energy.)
• During an interaction, energy can be transferred between objects. (For example, when you push a cart to start it moving, we say energy is transferred from you to the cart.)
• Energy cannot be created or destroyed, only transferred between objects, or transformed to different types within the same object.

Next: Explanations Using Energy Ideas – Assumptions of the Model