How to describe processes in terms of energy
Physics Narrative
for 11-14
Describing processes in terms of energy
You can develop an energy description using the following approach.
Select a part of the world to study: chose the process or change to analyse.
Define the before
and after
snapshots for the change that you want to study. If you choose different moments to take your snapshots, you'll end up describing different parts of the process.
Identify the energy stores between which energy is shifted during the process.
A simple example to consider
For example, the action of lifting an ornament onto a shelf and allowing it to fall back to Earth.
For our example, various start and end points are possible, defining two quite separate processes that jointly make up the action:
The lifting process
Start: Ornament on the ground
End: Ornament on the shelf
The falling process
Start: Ornament on the shelf
End: Ornament on the ground
For the lifting process, two energy stores are of interest:
- The chemical store associated with the lifting arm
- The gravitational store of the ornament in the Earth's field
Energy is shifted from the chemical store of your muscles to the gravitational store of the ornament in the Earth's field.
The general approach:
- Choose a change to study.
- Take a snapshot (before).
- Take a snapshot (after).
- Identify the stores.
- Produce an energy description based on this analysis.
