## Discipline-Specific Techniques

We often use animations as overlays or accompaniments to video clips. This allows us to add abstractions such as time-varying vector and scalar quantities. This helps the student to ‘see’ these quantities and to make the link between the world and the quantitative analysis of it. We think that this is a powerful technique: the expert already 'sees' these vectors or quantities in his/her vision of the physical world. By adding them here, we are giving the novice something akin to the 'vision' of the expert.

Here, a video of a mass-spring oscillator is accompanied by a displacement-time graph. It is a good way to show displacement-time graphs because the displacement here is vertical, as is the traditional displacement axis. Time elapses as the point moves along the x axis (or the reverse, if you will). The rotating animation figure is what physicists call a phasor – another way of representing the motion.

Comparing the left and right version shows the importance of linking quantities: here we use the dashed line.

The short film below shows some examples (taken from Physclips) of how we have combined film clips and animations to explain physical principles. When a physicist sees some series of events in the real world, s/he 'sees' not only the objects involved, but also a set of abstractions, such as time-varying scalar quantities like energy and vectors like force and momentum. We think that students find it helpful to see these quantities conntected to or superposed on the film clip.

Physics is an experimental science, so experiments are paramount. Film clips of experiments are less prefered, but are often easier to deliver via the web. Sometimes, however, one simply can't have a film clip: the scale might be too big (eg cosmology) or too small (particle physics) or too fast (relativity). Here animations can be helpful. The following short film uses some examples from our introduction to relativity to show how and why we have used cartoon-style animations to introduce some difficult ideas.