Chapter 1 – Conservation and Dissipation of Energy
1.1 – Changes in Energy Stores
Energy can be stored in a variety of different ways such as:
Chemical Energy :- for foods and fuels
Kinetic Energy :- the energy an object has because it is moving
Gravitational Potential Energy :- the energy an object has because of its position relative
to the ground
Elastic Potential Energy :- the energy it has because it is being squashed or stretched
Thermal Energy :- the energy it has because of its temperature
Energy can be transferred from one store to another
Energy can be transferred through waves, heating, an electric current, or when a force moves an
object
1.2 – Conservation of Energy
Energy cannot be created or destroyed. This is called the principle of conservation of energy
Energy can be dissipated, transferred usefully, or stored
A closed system is a group of objects where no energy transfers take place out of or into the
energy stores of the system
Energy can still be transferred between different stores within a closed system
In a closed system. The total energy of the system is always the same
1.3 – Energy and Work
Work is done on an object when a force makes the object move
Energy transferred = work done
Both work and energy use the unit Joule (J)
The work done on an object is calculated using W =F × s where :
W :- Work Done (Joules, J)
F :- Force (Newtons, N)
s :- Distance (metres, m)
Work done to overcome friction is transferred as energy to the thermal energy stores of the
objects that rub together and to the surroundings
1.4 – Gravitational Potential Energy Stores
The gravitational potential energy store of an object increases when it moves up and decreased
when it goes down
As an object is lifted up, work is done on it to overcome the gravitational force so the
gravitational potential energy increases
The gravitational field strength of the earth is 9.8 N/kg
gpe=m× g × Δh
Gpe :- gravitational potential energy (Joules, J)
M :- mass (kilograms, kg)
G :- gravitational field strength (N/kg)
Δh :- change in height (Metres, m)
1.1 – Changes in Energy Stores
Energy can be stored in a variety of different ways such as:
Chemical Energy :- for foods and fuels
Kinetic Energy :- the energy an object has because it is moving
Gravitational Potential Energy :- the energy an object has because of its position relative
to the ground
Elastic Potential Energy :- the energy it has because it is being squashed or stretched
Thermal Energy :- the energy it has because of its temperature
Energy can be transferred from one store to another
Energy can be transferred through waves, heating, an electric current, or when a force moves an
object
1.2 – Conservation of Energy
Energy cannot be created or destroyed. This is called the principle of conservation of energy
Energy can be dissipated, transferred usefully, or stored
A closed system is a group of objects where no energy transfers take place out of or into the
energy stores of the system
Energy can still be transferred between different stores within a closed system
In a closed system. The total energy of the system is always the same
1.3 – Energy and Work
Work is done on an object when a force makes the object move
Energy transferred = work done
Both work and energy use the unit Joule (J)
The work done on an object is calculated using W =F × s where :
W :- Work Done (Joules, J)
F :- Force (Newtons, N)
s :- Distance (metres, m)
Work done to overcome friction is transferred as energy to the thermal energy stores of the
objects that rub together and to the surroundings
1.4 – Gravitational Potential Energy Stores
The gravitational potential energy store of an object increases when it moves up and decreased
when it goes down
As an object is lifted up, work is done on it to overcome the gravitational force so the
gravitational potential energy increases
The gravitational field strength of the earth is 9.8 N/kg
gpe=m× g × Δh
Gpe :- gravitational potential energy (Joules, J)
M :- mass (kilograms, kg)
G :- gravitational field strength (N/kg)
Δh :- change in height (Metres, m)
