Context

Putting into context

To put a concept in context we need to see how it can be applied to real life situations. This can be slightly problematic in physics at this level since a lot of what we teach doesn't properly apply in real situations.

• A pendulum is only SHM if we ignore air resistance and consider small oscillations.
• The only example of constant acceleration we are ever likely to experience of free fall and that's not actually constant acceleration.
• Bouncing balls are rarely isolated.
• The Earths orbit around the Sun isn't circular.
• Mechanical energy isn't conserved as a block slides down a slope.
• Diffraction isn't the only thing that limits the resolving power of our eyes

It's true that students always seem to latch onto a topic if there is an interesting context, having seen a large hologram for the first time students will always want to know how it works, sometimes it's worth going beyond the syllabus to put something like interference into context.

The subject guide helps by giving examples of "utilisations" but I don't find these particularly useful.

• Forces are used in construction.
• Conservation of energy is used in electrical power generation.
• Conservation of momentum is used in martial arts.

I believe in playing to my strengths so tend to use examples that I am interested in and know something about, this often leads to some sidetracking but if it keeps the students awake all well and good.

• Impulse: falling on an elastic climbing rope.
• Friction: climbing shoes.
• Friction: car tyres.
• Air resistance: base jumping.
• Harmonics: Guitar playing (actually I can't play the guitar at all so this generally turns in to a comedy item).
• Waves: surfing.

It's sometimes difficult to understand the context before the concept so I often give examples after the theory.

Context can be practical or it can be imaginary. When teaching about time dilation we often give examples involving twins flying past each other or trains passing rabbits on stations. These are not real life situations but help us to understand the consequences of the theory. Without this fake context we would not fully understand the implications of the Lorentz transforms.

Simulations are another form of manufactured context. Within the context of Algodoo you can simulate resonance, this is not real but it follows the equations that we use to represent reality, using the simulation the student can understand how a mass on a spring behaves as it is forced to oscillate. Context doesn't have to be real life application, to put into context means to give extra information to help understand something better. Building a GeoGebra simulation based on the wave equation helps to understand how the equation relates to the wave motion.

Local and Global

The IB document specifies that teaching should be developed in local and global contexts. Most of the physics syllabus is concerned with phenomena that are fairly universal so the idea of local and global context is a bit difficult to apply. There are a few obvious examples in the section on energy production where it would not be out of place to discuss the local consumption of energy compared to global.

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