Forces and Motion

Lessons from this episode: describing forces

Physics Narrative for 11-14 Supporting Physics Teaching

Helpful approaches: a summary

When describing a situation using forces, aim to answer these questions:

  • What exerts the force?
  • What kind of force is acting?
  • What is the force acting on?

When drawing force diagrams, a helpful process is to:

  • Imagine you are looking through forces spectacles.
  • Focus on one object of interest.
  • Reduce this object of interest to its simplest representation. This can often be just a point.
  • Only then add the force arrows.

In many cases all the forces acting on an object will balance. The net effect is that nothing changes. We describe such objects as being in equilibrium.

What's to follow

Moving on from these key skills of representing forces and recognising that the forces acting on an object can be in equilibrium, we now turn to exploring kinds of forces in episodes 02 and 03. Thinking about these provides the justification for adding arrows to diagrams, so providing a force-spotter's guide. So far how to identify the forces acting on an object has not received sufficient attention. The next two episodes rectify that.

Episode 02 deals with the kinds of forces to look out for when two objects are in contact: kinds of contact forces.

Episode 03 deals with kinds of non-contact forces, sometimes called action at a distance forces.

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