Power to Choose rates

Energy conversation and rates


Traditional physics texts develop ideas and concepts in a hierarchical structure. Authors assume that the proper way to understand the subject is by working your way up through a web of ideas, from simple stuff at the bottom to higher concepts at the top. A serious defect in that approach to writing school-level physics is that by keeping got simple at the basic level we can also make it wrong.

Rate and reality

Understanding energy those to modify their knowledge inappropriate ways. Whatever you about the interpretation of this kind of research, it is very important that teachers should be aware of the ways that their students talk and think about energy. Power to Choose rates of itself does not cause anything. This kind of interpretation may be reinforced by teaching programs which, recognizing the importance of energy as a universal concept, go overboard by using energy as a universal explanation. The reality of the theories of physics is that energy itself has little explanatory power in telling exactly how nature behaves; it tells more about what is impossible. The conservation principle and the laws of thermodynamics restrict or constrain what can happen but they don’t determine it. To provide a solid foundation for the conceptions of energy that I will outline we need to establish a few other concepts, notably the ideas of a physical system and a frame of reference. We will also need to develop an understanding of the nature of scientific theory and of modelling.

A physical system can be any collection of things that we want to study, such as a moving car and its contents. Usually, we can mentally draw some kind of imaginary boundary around the system. Then everything outside the boundary can be considered as its environment. In the case of the car, the environment would include the road and the atmosphere. In a typical mechanics problem, we would construct an abstract model of the system by ignoring some features which might be quite important in other contexts, such as the fact that a car sucks in air and emits exhaust gases.

Depending on the problem, we might model the car as a solid object with four rotating wheels in contact with the road. The atmosphere might be modelled as a vague object which exerts a retarding force located at some point on the car. The connection between the ideas of energy and system is that it is often useful to think of the system as having energy and to study how the system may be exchanging energy with the rest of the universe.

Power to Choose rates

A frame of reference is provided by some object onto which we can tie a fixed system of co-ordinate axes and a time scale. The idea of a frame will be important for understanding the definitions of kinetic and potential energy. For more about frames find a chapter about relativity in your favourite text or see my article about Understanding Relativity in this volume.  Furthermore, even though it would be nice if the concept of energy were immutable, the history of physics shows that conceptions change. Ideas about energy are still developing and cropping up in new contexts. It is very important things for energy rates.