10_Energy

Energy

DEFINITION

• Energy is a property that must be
  transferred to an object in order to
  perform work on or heat up that object
  It is measured in units of Joules (J)
  Energy can be stored in different
  ways, and there are changes in the
  way it is stored when a system changes

Energy
Stores
Table

Analyze the energy!

Energy Transfer

Energy can be transferred
between stores through different
energy transfer pathways
Examples of these are:

Mechanical
Electrical
Heating
Radiation

.

Energy Transfer Table

A N E X A M P L E O F

A T H E R M A L

E N E R G Y

T R A N S F E R B Y
H E A T I N G , I S A

H O T C O F F E E
H E A T I N G U P
C O L D H A N D S

Thermal energy is

transferred by heating from

the hot coffee to the mug

and to the cold hands

"The principle of conservation of energy
states that:

"Energy cannot be created or destroyed, it
can only be transferred from one store to
another"

This means that for a closed system, the total
amount of energy is constant

Conservation of Enegry

​Simple

Diagram ​

Sankey diagram is a way
of using picture to show
how energy is going in to
a system, how much useful
energy is coming out, and
how much energy is lost
by system.

SANKEY
DIAGRAM

Sankey
Diagram

for

Electrical

Bulb

Energy
Calculations

Kinetic Energy

The kinetic energy, EK, of
an object (also known as its
kinetic store) is defined as:

This means that any object
in motion has energy in its
kinetic energy store

The energy an object has as a
result of its mass and speed

Kinetic energy can be calculated using

the equation:

EK = ½ × m × v^2

Where:

EK = kinetic energy in Joules (J)

m = mass of the object in kilograms (kg)

v = speed of the object in metres per second (m/s)

Calculate the kinetic energy
stored in a vehicle of mass 1200
kg moving at a speed of 27
m/s.?

E X A M P L E

Gravitational Potential Energy

The gravitational potential energy, EP, of an
object (also known as its gravitational store) is
defined as:

This means:

If an object is lifted up, energy will be
transferred to its gravitational store
If an object falls, energy will be transferred
away from its gravitational store

The energy an object has due to its height in a
gravitational field

A man of mass 70 kg climbs a
flight of stairs that is 3 m
higher than the floor.
Gravitational field strength is
approximately 10 N/kg.
Calculate the energy
transferred to his gravitational
potential energy store!

E X A M P L E