What is Energy?
Energy is one of the most fundamental ideas in all of science. You encounter it every single day — in the food you eat, the light from your phone screen, the warmth of the Sun, and the movement of every vehicle on the road.
The property that allows work to be done on an object. Energy gives objects the capacity to change or move, and it can be converted from one form into another.
Think of energy as the "ability to make things happen." Without energy, nothing would move, grow, heat up, or change. It is the invisible currency that powers the entire universe.
Think of energy like money in a bank account. You can transfer it to someone else, spend it on different things, and convert it into different forms — but the total amount in the system never disappears. You can't create money from nothing, and you can't destroy it either.
Systems thinking: Scientists often talk about a system — a defined group of objects that we are studying together. When we say energy is conserved, we mean the total energy within a closed system stays the same, even as energy moves between objects or changes form within that system. Choosing what to include in your system is an important scientific skill.
Forms of Energy
Energy comes in many different forms. Each form describes a different way that energy can be stored or transferred.
| Energy Form | Description |
|---|---|
| Kinetic energy | Energy possessed by moving objects |
| Gravitational potential energy | Energy stored by lifting an object upwards against gravity |
| Elastic potential energy | Energy stored by stretching or compressing a spring or elastic band |
| Chemical energy | Energy stored in the chemical bonds of substances (e.g. food, fuel) |
| Thermal energy | Energy stored in the random motion and vibration of particles within a substance; the greater the thermal energy, the higher the temperature |
| Electrical energy | Energy carried by moving electric charges |
| Nuclear energy | Energy stored in the nucleus of an atom (studied in more depth in later years) |
| Electromagnetic energy | Energy carried by light and other electromagnetic waves |
You should be able to define and give examples of all the forms listed above. However, in this unit the calculations will focus on three mechanical forms: kinetic energy, gravitational potential energy, and elastic potential energy. Make sure you are confident with all three of these.
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