MOVEMENT AND CHANGE
Forms of energy Gravitational potential energy
FORMS OF ENERGY
There are several forms of energy.
Thermal energy
Caused by the movement energy of molecules.
FORMS OF ENERGY
Kinetic energy (KE)
This is the energy all moving objects have.
A moving lorry has lots of kinetic energy!
FORMS OF ENERGY
Chemical energy
Energy which is stored in food or fuels
FORMS OF ENERGY
Sound and light energy
Common types of energy
FORMS OF ENERGY
Electrical energy
Very common and useful
(Magnetic energy is always connected with electrical energy)
FORMS OF ENERGY
Nuclear energy
Energy stored in the centre of the atom
FORMS OF ENERGY
Gravitational potential energy
When an object is moved to a higher place it gains stored energy which it can give out if it falls down.
The Principle of Conservation of Energy
Energy can be changed from one form to another but it cannot be created or destroyed.
Falling under gravity
A diver may use 6000J of energy climbing to the top of a board. At the top of the board he has 6000 J of gravitational potential energy (PE) but no kinetic energy (KE). As he dives, his PE is converted into an equal amount of KE
Falling under gravity
The total amount of PE + KE is always 6000J!
The Pendulum
The Pendulum
When a pendulum swings to and fro, its energy is constantly changing from potential energy (PE) to kinetic energy (KE) and back again.
The Pendulum
The energy eventually is converted to heat by friction with the air. This heat is “low grade” energy and we can not make use of it All energy eventually becomes low grade.
Calculating Potential Energy
For a weight lifter lifting a mass of 200 kg up a height of 2 m we can work out the gain in potential energy. Potential energy = work done = weight x height lifted
Calculating Potential Energy
On Earth weight (in N) = mass (in kg) X 10 so:
PE = mass x 10 x height
Calculating Potential Energy
Gravitational PE = mass x g x height (in joules) (kg) (N/kg) (m)
On Earth g = 10, but g has different values on other planets