GCSE Physics Exam Preparation: Systems
In GCSE Physics, a system is an object or a group of objects that we choose to study. Everything outside the system is known as the surroundings. In exam questions, clearly identifying the system is essential for accessing full marks.
A system can be open or closed. In a closed system, energy can be transferred in or out, but matter does not enter or leave. At GCSE level, most energy calculations assume a closed system. The key principle you must apply is the law of conservation of energy:
Energy cannot be created or destroyed; it can only be transferred between energy stores.
You should be confident with the main energy stores:
- Kinetic
- Thermal (internal)
- Gravitational potential
- Elastic potential
- Chemical
- Magnetic
- Electrostatic
- Nuclear
In exam questions, you are often required to:
- Define the system
- Identify the energy stores involved
- Describe how energy is transferred
- Explain where energy is dissipated
For example, when a ball falls:
If the system is the ball and the Earth, gravitational potential energy decreases and kinetic energy increases. Some energy is transferred to the thermal energy store of the surroundings due to air resistance. The total energy of the system remains constant.
Avoid saying “energy is lost.” Energy is not lost; it is transferred to less useful energy stores, usually the thermal store of the surroundings.
A strong exam sentence would be:
In a closed system, the total energy remains constant because energy is conserved and only transferred between energy stores.
Always be precise, name the energy stores correctly, and clearly define the system. This clarity is what examiners reward.