Examples of Energy Transfer (AQA GCSE Physics): Revision Note
Exam code: 8463
Energy Transfer Examples
Different types of energy transfers occur all the time in various everyday circumstances
Some common situations include
When an object is projected upwards
When a moving object hits an obstacle
When an object is accelerated by a constant force
When a vehicle speeds up or slows down
When water is brought to a boil in an electric kettle
An object projected upwards
Before the ball is thrown upwards, the person holding the ball has energy in their chemical store
When the ball is thrown, some of that energy is transferred to the kinetic store of the ball as it begins to move upwards
As the height of the ball increases, energy from the kinetic store of the ball is transferred to its gravitational potential store
As the ball rises, the energy in its kinetic store decreases and the energy in its gravitational potential store increases
At the highest point, the ball is momentarily stationary, so its kinetic store is at a minimum, and its gravitational potential store is at a maximum
As the ball falls back down, energy is transferred from the gravitational potential store back to the kinetic store
Examiner Tips and Tricks
In 'describe' questions on energy changes, say whether each store increases or decreases, or that energy is transferred from one store to another. Naming the stores alone does not score. Write 'gravitational potential' or 'elastic potential' in full, because 'gravitational energy' on its own is not credited
A moving object hitting an obstacle
When an object, such as a car, is moving, energy in the chemical store of the fuel is transferred to the kinetic store of the car
If the object hits an obstacle, such as the car hitting a wall, the speed of the car will decrease very quickly
Therefore, the energy in its kinetic store will decrease
In this scenario, most of the energy from its kinetic store is transferred to the thermal store of the surroundings (dissipated)
Energy is transferred mechanically to the thermal store of the wall (the force of the car on the wall)
Some energy is transferred by heating to the thermal store of the car and the wall
Some energy is transferred away by sound waves, which make the air particles vibrate and increase the thermal store of the air
A vehicle being accelerated by a constant force
When a vehicle is stationary, it has energy in the chemical store of the fuel
When the vehicle speeds up or accelerates, the energy is transferred to the kinetic store of the car
The same transfer happens when a person accelerates, for example, a cyclist
Energy in the chemical store of the cyclist's body decreases, and energy in the kinetic store of the cyclist increases
On a flat road, the gravitational potential store does not change
Examiner Tips and Tricks
On a flat road, a cyclist's gravitational potential energy stays the same, so do not choose it as the store that decreases
A vehicle slowing down
When a vehicle is moving, it has energy in its kinetic store
As it slows down or decelerates, energy is transferred from the kinetic store of the vehicle to the thermal store of the brakes
This is energy transferred mechanically, because friction between the brake pads and the brakes does work on the wheels
The brakes then transfer energy by heating to the thermal store of the surroundings (dissipated)
Friction between the tyres and the road transfers some energy to the thermal store of the tyres and road in the same way
Energy is also transferred away by sound waves, which make the air particles vibrate
Boiling water in a kettle
When an electric kettle boils water, energy is transferred by electrical working from the mains to the thermal store of the heating element inside the kettle
As the heating element gets hotter, energy is transferred by heating to the thermal store of the water
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