AQA Physics (8463) 4.1.1.1 · Model
Energy stores and systems
Triple Science · Higher tier
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If you had to guess, what happens to the energy of a ball as it rises after you throw it?
Key words
- system
- energy store
- energy transfer
Key knowledge
A system is an object or group of objects.
When a system changes, there are changes in the way energy is stored.
- Kinetic: a moving object.
- Gravitational potential: an object raised above the ground.
- Elastic potential: a stretched or compressed object.
- Thermal: any object. Hotter objects store more.
- Chemical: food, fuel and batteries.
- Magnetic, electrostatic and nuclear.
How energy is stored as a system changes
| Row | What changes |
|---|---|
| An object projected upwards | |
| A moving object hitting an obstacle | |
| An object accelerated by a constant force | |
| A vehicle slowing down | |
| Bringing water to a boil in an electric kettle |
Energy is transferred between stores in three ways you can calculate:
- by heating
- by work done by forces
- by work done when a current flows
A ball leaves your hand with 20 J in its kinetic store.
At its highest point it has 18 J in its gravitational potential store.
The other 2 J has been dissipated to the surroundings.
20 J = 18 J + 2 J. The total is the same before and after.
Wrong: Energy gets used up.
Right: Energy moves from one store to another.
Wrong: Heating is a store of energy.
Right: Heating is a way of transferring energy. Thermal is the store.
Key fact
A system is an object or group of objects. When a system changes, energy moves between stores by heating, by work done by forces or by work done when a current flows.
Energy can also be carried by waves, such as light and sound.
You will meet these in the waves topic.
- Describe: name each store in order as it empties or fills.
- Calculate: work out a number and show each line.
- Explain: say what happens and why.
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