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The building sector is a big consumer of energy and is responsible for a considerable share of the greenhouse gas emissions within most developed countries. Based on the development in underlying drivers and using system analysis methods, the historical development in energy flows in the Norwegian residential building stock, the associated costs and greenhouse gas emissions are estimated. The results show that although a 39% decrease occurred in energy consumption per square metre in the use phase, the total energy consumption increased due to increased stock size. Further, the total energy consumption was substantially dominated by the use phase. The energy-related costs increase even more than energy consumption due to increased energy prices, but the greenhouse gas emissions decrease due to changes in the energy mix. The per-capita results follow the same trends as the aggregated results, whereas there have been larger improvements in the system on a per-square-metre basis. Based on underlying drivers, the model ensures inclusion of development trends that are not easily explained by the direct factors energy efficiency, energy mix and energy prices. Le secteur du batiment est un gros consommateur d'energie et est responsable d'une part considerable des emissions de gaz a effet de serre dans la plupart des pays developpes. En se basant sur l'evolution des facteurs sous-jacents et en utilisant des methodes d'analyse des systemes, sont estimes l'evolution historique des flux d'energie dans le parc bati residentiel norvegien, les couts qui s'y rapportent et les emissions de gaz a effet de serre. Les resultats montrent que, bien qu'une diminution de 39% soit intervenue dans la consommation d'energie par metre carre dans la phase d'utilisation, la consommation totale d'energie a augmente en raison de la taille accrue du parc. En outre, la consommation totale d'energie a ete fortement dominee par la phase d'utilisation. Les couts lies a l'energie augmentent encore plus que la consommation d'energie du fait de l'augmentation des prix de l'energie, mais les emissions de gaz a effet de serre diminuent en raison des changements intervenus dans le mix energetique. Les resultats par personne suivent les memes tendances que les resultats agreges, alors que des ameliorations plus importantes se sont produites dans le systeme sur la base du metre carre. En se basant sur les facteurs sous-jacents, le modele assure l'inclusion de tendances evolutives qui ne s'expliquent pas facilement par les facteurs directs d'efficacite energetique, de mix energetique et de prix de l'energie. Mots cles: parc bati, empreinte carbone, analyse des couts, parc de logements, analyse dynamique des flux de materiaux, empreinte economique, consommation d'energie, efficacite energetique, emissions de gaz a effet de serre [ABSTRACT FROM AUTHOR]

In the teaching of physics at upper secondary school level (K10–K12), the students are generally taught to solve problems analytically, i.e. using the dynamics describing a system (typically in the form of differential equations) to compute its evolution in time, e.g. the motion of a body along a straight line or in a plane. This reduces the scope of problems, i.e. the kind of problems that are within students’ capabilities. To make the tasks mathematically solvable, one is restricted to very idealized situations; more realistic problems are too difficult (or even impossible) to handle analytically with the mathematical abilities that may be expected from students at this level. For instance, ordinary ballistic trajectories under the action of gravity, when air resistance is included, have been ‘out of reach’; in school textbooks such trajectories are generally assumed to take place in a vacuum. Another example is that according to Newton’s law of universal gravitation satellites will in general move around a large central body in elliptical orbits, but the students can only deal with the special case where the orbit is circular, thus precluding (for example) a verification and discussion of Kepler’s laws. It is shown that standard spreadsheet software offers a tool that can handle many such realistic situations in a uniform way, and display the results both numerically and graphically on a computer screen, quite independently of whether the formal description of the physical system itself is ‘mathematically tractable’. The method employed, which is readily accessible to high school students, is to perform a numerical integration of the equations of motion, exploiting the spreadsheet’s capability of successive iterations. The software is used to model and study motion of bodies in external force fields; specifically, ballistic trajectories in a homogeneous gravity field with air resistance and satellite motion in a centrally symmetric gravitational field. The article reports briefly on a study of the use of computers in the teaching of physics at K12 level in Norway, as part of an EU research project (for details, see the end of the article). It is demonstrated how the simulation software (the spreadsheet) is implemented in practice, for the systems that have been studied, and various responses of the students and teachers to this new and unfamiliar method for solving problems in physics are discussed. Some perspectives on the future of physics teaching at secondary school level are discussed. [ABSTRACT FROM AUTHOR]