OCR · GCSE · Physics
Course version: J249 · Version from Sept 2018
Describe all the changes involved in the way energy is stored when a…
Full specification wording
Work done: describe all the changes involved in the way energy is stored when a system changes for common situations (to include: an object projected upwards or up a slope, a moving object hitting an obstacle, an object being accelerated by a constant force, a vehicle slowing down, bringing water to a boil in an electric kettle)
Energy is conserved, but it moves between stores.
Checked against the OCR J249 specification (opens in a new tab) on .
- Point 2 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Energy is conserved, but it moves between stores. For each named situation, track the store that empties and the store that fills. An object projected upwards or up a slope gains gravitational potential energy as it rises and loses kinetic energy as it slows; at the top the kinetic store is momentarily empty. A moving object hitting an obstacle transfers kinetic energy to thermal energy in the object and obstacle, plus sound. An object accelerated by a constant force has work done on it, so its kinetic store grows while the force's source store (for example chemical in a fuel) empties. A vehicle slowing down transfers kinetic energy to thermal energy in the brakes and surroundings. In an electric kettle, the chemical store of the supply empties, energy is transferred electrically to the heating element, and the water's thermal store rises until it boils.
What earns the marks
- Identifies the store that empties and the store that fills for each named situation.
- States that a rising object transfers kinetic energy to gravitational potential energy.
- States that a collision transfers kinetic energy to thermal energy and sound.
- States that a constant force does work that increases an object's kinetic energy.
- States that a slowing vehicle transfers kinetic energy to thermal energy in the brakes.
- States that a kettle transfers energy electrically from the supply to the water's thermal store.
Common mistakes and how to put them right
Says energy is used up or destroyed.
Put it right: State that energy is conserved and only transferred between stores.
Claims a rising object gains kinetic energy.
Put it right: State that it loses kinetic energy and gains gravitational potential energy.
Treats the kettle as creating energy.
Put it right: State that energy is transferred electrically from the supply to the water.
Exam tips
- Name both the store that empties and the store that fills for each situation.
- Use the words kinetic, gravitational potential, thermal and chemical precisely.
- Check whether the question asks for one situation or all five before answering.
Try the lesson
The start of the Work done: describe all the changes involved in the way energy is stored when a system changes for common situations (to include: an object projected upwards or up a slope, a moving object hitting an obstacle, an object being accelerated by a constant force, a vehicle slowing down, bringing water to a boil in an electric kettle) lesson, made from checked teaching notes for this specification point.
Have a go first
A ball is thrown vertically upwards and rises until it stops momentarily at its highest point. Ignoring air resistance, how does the energy stored in the ball–Earth system change during the rise?
Listen
Energy is conserved, but it moves between stores. For each named situation, track the store that empties and the store that fills. An object projected upwards or up a slope gains gravitational potential energy as it rises and loses kinetic energy as it slows; at the top the kinetic store is momentarily empty. A moving object hitting an obstacle transfers kinetic energy to thermal energy in the object and obstacle, plus sound. An object accelerated by a constant force has work done on it, so its kinetic store grows while the force's source store (for example chemical in a fuel) empties. A vehicle slowing down transfers kinetic energy to thermal energy in the brakes and surroundings. In an electric kettle, the chemical store of the supply empties, energy is transferred electrically to the heating element, and the water's thermal store rises until it boils. A strong answer earns marks for these points. Identifies the store that empties and the store that fills for each named situation. States that a rising object transfers kinetic energy to gravitational potential energy. States that a collision transfers kinetic energy to thermal energy and sound. States that a constant force does work that increases an object's kinetic energy. Exam tip: Name both the store that empties and the store that fills for each situation.
Key words
Say what each word means before you turn the card.
Conservation of energy
Try answering aloud or in your head before turning the card.
Energy stores and transfers
Try answering aloud or in your head before turning the card.
Work done by forces
Try answering aloud or in your head before turning the card.
Everyday energy changes
Try answering aloud or in your head before turning the card.
See every definition
- Conservation of energy
- Energy is conserved, but it moves between stores; it is not used up or destroyed, only transferred between stores.
- Energy stores and transfers
- For each named situation, track the store that empties and the store that fills as energy moves between them.
- Work done by forces
- An object accelerated by a constant force has work done on it, so its kinetic store grows while the force's source store empties.
- Everyday energy changes
- In common situations, such as a rising object, a collision, a slowing vehicle or a kettle, energy is transferred between kinetic, gravitational potential, thermal and chemical stores.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Work done: describe all the changes involved in the way energy is stored when a system changes for common situations (to include: an object projected upwards or up a slope, a moving object hitting an obstacle, an object being accelerated by a constant force, a vehicle slowing down, bringing water to a boil in an electric kettle)
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge