Force, Motion and Energy
Year 9 Extension Science
GZ Science Resources 2014
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1a
GZ Science Resources 2014
The different types of motion
Objects that move from one point of
space to another over time are said to
have motion. Examples include a tortoise
slowly moving across the ground or a
bullet moving fast after it has been fired
from a gun. Objects that remain at the
same point of space over a period of time
are called stationary. Examples include a
person sitting still on a chair or a parked
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car.
1a
Speed is a measure of motion
Speed is a measure of the distance travelled over the time taken. The more
distance covered by an object during a given time, the faster the speed it is
moving.
Constant speed occurs when the object travels the same amount of distance
at each even time period. When we travel on an object moving at a constant
speed we do not feel movement for example travelling in an airplane .
Only when we observe other objects
moving at a different speed to us do
we notice that we are moving.
NOTE: in this unit we
also use the symbol
V to stand for speed
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1a
The relationships between distance, time and speed
Triangles can be used
to calculate speed,
distance or time.
Cover the part of the
triangle you wish to
calculate and
multiply or divide the
remaining two values.
The unit for speed
depends upon the
units for time and
distance but the most
common unit in the
lab is metres per
second (ms-1)
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1b
Measuring Motion in Science
Quantity
Unit
Symbol
Equipment used
Distance
Kilometre
km
odometer
Metre
m
Metre ruler
millimetre
mm
Hand ruler
Hour
hr
clock
minute
min
watch
second
s
Stop watch
Time
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1b
Converting measurements
Quantities are often measured in different
scales depending upon what is most
appropriate for the original size. In Science
(and Mathematics) we use common
prefixes to indicate the scale used.
We sometimes want to convert scales from
one to another to compare data or to
place the measurements into equations.
Prefix
Scale
Kilo = 1000
Centi = 1/100th
Milli = 1/1000th
So 1 kilometre = 1000 metres
1 metre contains 100 centimetres
1 metre contains 1000 millimetres
To convert from metres to kilometres divide by 1000
To convert from kilometres to metres multiply by 1000
Time is measured in “imperial units” 1 hour has 60 minutes and 1 minute has 60
seconds therefore 1 hour has 3600 seconds
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1b
Errors may occur in measurements may be reduced by taking the
average of a number of readings
When collecting and measuring data in investigations, such as that for calculating speed,
errors can occur. This may be due to the measuring instrument and the way it is used.
Data can also be recorded incorrectly.
Repeating the investigation a number of times and averaging out the measurements can
help reduce random errors. This value is called the mean.
Distance walked in 1 minute
The mean is the most
common measure of
average.
To calculate the mean add
the numbers together and
divide the total by the
amount of numbers:
Mean = sum of numbers ÷
amount of numbers
GZ Science Resources 2014
Distance
(m)
Trial 1
Trial 2
Trial 3
113
121
119
Mean = (113 + 121 + 119 ) ÷ 3
= 117.7 m
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1c
Acceleration is a change in velocity
Objects that have a change in velocity are said to have acceleration.
An increase in velocity or
a decrease in velocity
(deceleration) are both
types of acceleration.
A change in direction
while travelling a
constant speed is also
acceleration. We notice
when we are travelling on
an object that is
accelerating by
experiencing a change in
gravity or G-force.
GZ Science
Year
10 Science
Resources
2012 2014
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1c
Speed and acceleration
acceleration = change of velocity
time taken
aaverage = Δv
Δt
The units for Acceleration depend on what velocity and time are measured in.
If time is measured in seconds (s) and velocity is measured in metres per second
(ms-1) then the units for acceleration with be metres per second per second
(ms-2)
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1d
Factors effecting stopping distance
The Stopping distance of a vehicle is the total distance travelled from the time the driver
registers they have to stop to the actual stopping point. The reaction time (1.5seconds) is
the average time a driver takes to apply the brakes. The main factor affecting the
stopping distance is the speed the vehicle is travelling at before the brakes are applied.
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1d
Factors effecting stopping distance
Other factors that increase stopping distance include a wet road, low tread on a tyre and
worn brakes. These factors decrease friction and therefore the kinetic energy of the car
(making it move) is transformed into heat energy at a slower rate.
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GZ Science Resources 2014
1e
Speed and Velocity
Velocity measures the speed of an object and the direction it travels. Two
objects can have the same speed but different velocities if they are not
travelling the same direction. An object can have a constant speed but its
velocity can change if it does not travel in a straight line.
This car has a change in velocity because it is
traveling around a corner even though it has
constant speed.
extension
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2a
Motion can be represented graphically - Distance vs Time
Distance verses Time graph
Distance (y axis) and time (x
axis) data can be plotted on a
graph to show patterns and
compare speeds.
The steeper line on the left
shows student A has a faster
speed than student B.
A straight diagonal line
indicates constant speed. A
straight horizontal line
indicates the object is
stationary .
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2a
Motion can be represented graphically – Distance vs Time
Distance verses Time graph
A distance time graph
can also show
acceleration with a
curved line (blue)
because at each time
interval the distance
travelled becomes larger
and larger.
Changes in speed are
also shown with a
combination of diagonal
and horizontal lines
(red).
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2a
Velocity (speed) can be calculated from a Distance-time graph
Distance verses Time graph
A distance - time graph can be used to
calculate speed (velocity). The coordinates of a straight line in the graph
are taken (for example from A to B) by
projecting back to the x and y axis.
Distance (metres)
To calculate the value for time find the
difference between t1 and t2 by
subtracting the smallest value from
the largest value. This will be your
time.
Repeat to find distance on the y axis.
This will be your distance.
Time (seconds)
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Place both values into your formula to
calculate speed (velocity)
v = d/ t
2b
Motion can be represented graphically – Velocity vs Time
Velocity verses Time graph
A velocity time graph can show
acceleration with a diagonal
line.
Constant velocity is shown with
a straight horizontal line.
Values can be taken from the
graphs and used to calculate
acceleration.
The blue line shows a velocity
of 10ms-1 travelled in 2
seconds.
The acceleration would
therefore be:
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a = ∆v/ t
= 10/2
a = 5ms-2
2b
Graphs may be used to display motion/time relationships
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2c
Distances travelled can be calculated from the area under a
velocity-time graph
The total distance can be calculated
from a velocity time graph by
calculating the area under the graph.
Work out the area of each triangle
(1/2 height x width) and add to the
area of the rectangle (height x width)
Velocity verses Time graph
velocity
For example:
d = (½ 8 x 6) + (1/2 8 x 4) + (8 x 12)
d = 24 + 16 + 96
d = 136seconds
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extension
GZ Science Resources 2014
3a
Force can cause an object to change its velocity or to deform.
Forces push, pull, tug, heave, squeeze, stretch, twist or press.
Forces change:
The shape of an object
The movement of an object
The velocity of an object
Not all forces can be seen but
the effects can be measured.
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3a
Force is measured in Newtons
Isaac Newton was born in
1642 in England. He
created laws of motion and
gravity.
Isaac Newton used three
laws to explain the way
objects move and how force
acts upon them. They are
often called Newton’s
Laws.
The units of force are
named after this scientist
and are called Newtons.
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3a
Newton’s Laws
First Law
If the forces acting on an object are balanced, then the object will
remain stationary or carry on at the same speed in the same
direction.
Force one
STATIONARY
Force two
Balanced forces
Wind resistance
Engine force
Road friction
Constant speed
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SJ Gaze
3a
Newtons Laws
Second Law
If unbalanced forces act on an object, then the object will
accelerate in the direction that the net force acts.
Un-Balanced forces
Force two
Direction of acceleration
Force one
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SJ Gaze
3a
Newtons Laws
Third Law
When a force acts on an object, an equal and opposite reaction
force occurs. This is called action-reaction.
Action force
Reaction force
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SJ Gaze
1b
3b
Units of Force, Motion and Energy in Science
Quantity
Unit
Symbol
Equipment used
Force (weight)
Newton
N
Spring balance
Mass
Kilogram
kg
scales
Motion
Kilometres per
hour (velocity)
khr-1
odometer
Metres per
second (velocity)
ms-1
Ticker timer
Metres per
second per
second
(acceleration)
ms-2
Ticker timer
Joule
j
Energy
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3c
The effects of balanced and unbalanced forces
If all four forces acting on an
object are equal they are
said to be balanced.
Weight force
(gravity)
Friction force
Thrust (resultant
force)
Support force
(reaction force)
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SJ Gaze
In the absence of an unbalanced force an object will either remain at rest
or travel with a constant velocity
3c
When sky divers reach terminal velocity
they are traveling at a constant speed.
The forces of gravity accelerating the
skydiver towards earth are matched
exactly by the force of friction from the
air particles pushing against the skydiver.
If the person wears a more aerodynamic
suit or points their body downwards so
there is less surface area to act against
the air which reduces friction then the
terminal velocity will be faster.
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3c
Unbalanced forces change motion
Balanced forces cause no change in speed or direction, since they exert equal,
but opposite, push/pull effects on an object. Unbalanced forces can change the
speed and/or direction of an object
Direction of
flight
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3d
Unbalanced forces change motion
An object experiencing unbalanced force will accelerate in the direction of the largest
force. The net force can be calculated by subtracting the smaller force from the larger
force.
Force one = 30N
Force two = 120N
Net force = 120N – 30N = 90N pushing the object from right to left
Net force
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3e
Friction often provides opposing force acting on moving bodies
Friction occurs when one surface
moves against another. Friction
always opposes force.
When friction occurs, kinetic
energy from movement is changed
into heat energy.
Smooth surfaces create less friction
than rough surfaces. Friction that
occurs between air or water and a
solid body is called resistance.
Close-up
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SJ Gaze
3e
Sometimes friction is useful, at other times it is unhelpful.
Situations where Friction is unhelpful
Situations where Friction is useful
situation
Increased by
situation
decreased by
walking
Having grip on the
soles of your shoes
Friction in
bearings
Oil around bearings
cycling
Wider tyres with
tread
Drag on car
Aerodynamic
design to reduce
drag
driving
Good tread on
tyres. Brake pads
Drag on
snowboard
Smooth laquered
surface
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3f
The relationship between force, mass and acceleration given by the
equation F = ma
The Force experienced by an object can be
calculated by multiplying the mass of the
object by its acceleration.
Force = Mass x Acceleration
If more force is applied to an object then it
will accelerate faster
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extension
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3f
Acceleration of a body depends both on its mass and on the size of the
unbalanced force acting on it
Force = Mass x Acceleration
If the same amount of force is applied to two similar objects that have
different mass then then smaller object will accelerate faster.
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extension
GZ Science Resources 2014
4a
Mass and weight
All objects have Mass. Mass refers to the amount of atoms in an object.
The formula symbol for mass is m.
Mass is measured in grams (g) or kilograms (kg). 1kg = 1000g
The mass of the object remains the same regardless of its location.
The weight of an object depends
on its location and the gravity
pulling down on it.
The weight of an object can
change depending on where it is
located. Astronauts weigh less on
the moon because the force of
gravity is less, but their mass is
the same in both locations.
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4a
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Mass and weight
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Gravity is a force which acts between bodies even though they are not in
contact
4b
Objects create a gravitational field around them
>the bigger the object; the stronger the field
>the further away from the object, the less gravitational pull
Any other object within the field is pulled to the center of the mass:
>accelerating
>feeling weight
Strong pull
Weakest
pull
Not so strong
pull
SJ Gaze
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4c
The Earth is the source of a gravitational field
Isaac Newton was also famous for his work on
gravity. His law of universal gravitation states
that objects with mass attract each other with
a force that varies directly as the product of
their masses and decreases as the distance
between them increases.
This gravitation force causes objects to
accelerate towards the centre of the Earth
(remember F = m x a). Once they reach solid
ground the support force prevents them
falling any further. Because we also have mass
the Earth feels a gravitational attraction and
accelerates towards us but our mass is so tiny
compared to the Earth and the effect is not
noticed.
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extension
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4c
The Earth is the source of a gravitational field
The mass of the Earth creates an acceleration of 9.82 ms-2 for objects falling
towards it. Regardless of the size of the object, they all fall with the same
acceleration - only the shape, which causes changes in air resistance, causes
some objects to experience more opposing force and accelerate slower.
To calculate our weight, which is a force on an object in a gravitational field,
we multiply our mass by the gravitational acceleration of Earth (9.82ms-2)
Force = mass x acceleration
Weight = mass x gravity
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extension
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5a
The links between forces and energy
When a force is applied to an object of
mass and moves it over a distance then
work has been done.
Work is measured in joules.
To do 1 joule of work you need 1 joule of
energy.
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extension
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Work = force x distance
W= f x d
5b
The links between forces and energy
Power is a measure of work done over time.
Power is measured in units called watts.
Force = 20N
Power = work/time
P = w/t
Time = 25seconds
Distance = 5 metres
A car is pushed with a force of 20N and travels 5 metres.
The work done is w = f x d w = 20 x 5 = 100 joules
The power used to push the car is p = w/t p = 100/25 = 4 watts
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extension
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5c
Kinetic energy
An object has kinetic
energy when it is moving.
Kinetic energy that an
object contains depends
upon both its mass and
the velocity that it is
moving.
An object with more mass
will possess greater
kinetic energy than an
object with less mass that
is traveling at the same
velocity.
Kinetic energy = 0.5 x mass x velocity2
KE = (0.5) x (m) x (v)2
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extension
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5c
Kinetic energy
An object that has the same
mass as another but is
travelling at a greater
velocity will contain far more
kinetic energy.
This can be demonstrated by
two similar vehicles hitting a
stationary object. A vehicle
travelling at 100km per hour
will release a much greater
amount of kinetic energy on
impact compared to a
vehicle only travelling at
50km per hour.
Kinetic energy = 0.5 x mass x velocity2
KE = (0.5) x (m) x (v)2
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extension
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6a
Energy makes things happen
Energy is not a substance
or an object that you can
touch or hold, but
substances and objects
can possess energy
Energy is something that
is required to make things
change
Energy is needed to make
objects move or change
their state
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6a
Energy makes things happen
Any change in speed, size, shape or
temperature in an object requires
energy.
Energy is the ability to do work.
Work is applying force to an object and
making it move in distance.
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6a
Energy is measured in a unit called a joule (J).
A Joule, unit of work or energy, is equal to the work done by a force of one
Newton acting through one metre. This unit is named in honour of the
English physicist James Prescott Joule.
W (work) = F (force) x d (distance)
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6a
Power is measured in a unit called a watt (w).
Power is a measure of energy use. Power is how
quickly energy is being used which is called the rate of
energy use.
Power is the amount of energy used in a period of
time and the units are called watts.
1 joule of energy for 1 second = 1 watt of power
1 watt of power for 1 second = 1 joule of energy
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6b
Energy can exist as Chemical potential, Gravitational potential, Elastic
potential, Kinetic, Sound, Electrical, Light, Heat
Energy can be classified into two
types; kinetic energy (KE) and
potential energy (PE)
Kinetic energy is seen when
particles, waves or objects move
All forms of stored energy are
called potential energy – this can
not be seen until it is transformed
(changed) into active energy
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6b
Kinetic energy is seen when particles, waves or objects move
Light
(radiant)
Energy
Energy
traveling in
waves, with
wavelengths
that can be
seen by
humans.
Sound
Energy
Sound travels
in waves of
different
pressure. This
causes
movement of
particles.
Sound cannot
travel in a
vacuum.
Mechanical
kinetic
Energy
Movement
energy. This
can be seen
when matter
changes its
position in
space
Heat
(thermal)
Energy
Electrical
Energy
The kinetic
energy that
atoms contain.
The more they
move the
more heat
they contain.
Measured by
temperature
Energy
contained in
electrons. This
can either be
static like
lightning or
current
electricity that
moves in a
circuit.
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6b
All forms of stored energy are called potential energy
Gravitational
Energy
Elastic
Energy
Nuclear
Energy
Chemical
Energy
This is the
energy
contained by
an object
which pulls it
back to Earth.
The further up
from the
ground the
more it
contains.
Found in
springs,
rubber bands
etc. The more
they are
compressed
the more
energy they
contain to
make them
change back
to their
original shape
The energy
contained by
the nucleus of
an atom which
holds the
neutrons and
protons
together. A lot
of energy is
released when
these are
separated in a
nuclear
reaction
The energy
contained in
the bonds of
chemical
molecules –
i.e.food or
battery acid.
When these
bonds are
broken in a
chemical
reaction then
their energy is
released
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Geothermal
Energy
Energy
produced by
geological
processes of
the Earth
which causes
heat and
pressure to
rise to the
surface.
Magnetic
Energy
Energy
contained by a
magnet to
either attract
or repel other
magnetic
objects. It can
also cause
electrical
currents.
7a
Energy is always conserved.
Energy can not be created or destroyed, it can only
be changed from one form to another.
The total amount of energy
never changes. Energy is able to
transform from one type to
another. All types of potential
energy must be transformed
into kinetic energy in order for
work to be done.
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7b
Energy can be transformed from one type to another
Energy can be transferred from one
object to another. e.g. heat energy
from the rocks cooking the food in a
hangi. The type of energy does not
change
Energy can be transformed from one
type into another. e.g. electrical energy
changed into heat and sound energy
when boiling a jug.
One type of energy can be
transformed into many different types.
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7b
Energy can be transformed from one type to another
Any object lifted upwards gains in
gravitational potential energy. This
gravitational energy transforms back
into kinetic energy when it is
released or no longer supported.
Hydroelectric power stations use the
gravitation potential energy of water
to flow downwards through a
spillway and move turbines.
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All bonds that hold atoms, ions and
molecules together contain
chemical potential energy. When
these bonds are broken or the
atoms form molecules of lower
energy then heat energy is released.
Respiration in our cells involves
releasing energy that is contained
within the bonds of glucose
molecules.
7b
Energy can be transformed from one type to another
Batteries contain energy in the form
of chemical potential energy. When
a complete circuit is connected to
the terminals then chemical
reactions take place and the
potential energy is transformed into
electrical energy.
Sunlight produces radiant energy in
the form of thermal heat and light
energy. Only light energy is used by
plants and it is transformed into
chemical potential energy through
the process of photosynthesis.
Chloroplasts in the leaves contain a
chemical called chlorophyll that
captures the light.
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8a
Renewable and Non-Renewable Energy
Energy types can also be divided into renewable and non renewable energy. Renewable
energy sources can be used continuously with out running out. Renewable energy is
available in unlimited amounts and technology has developed so we can convert it into
electricity, heat and fuel for human use.
Non-renewable energy resources have often taken many millions of years to form and
they are in limited supplies. Once they have been used up they can not be replaced.
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8a
Renewable Energy
Energy is generated by the sun,
and is stored in a variety of
forms. It is locked into biomass
through the process of
photosynthesis. Burning
biomass releases energy, as
does decomposing biomass.
Energy is stored in the oceans
and fresh water where the
movement of the earth and
gravity release it through tides
and flowing rivers. The earth’s
spin generate waves and wind.
Heat created from the center of
the Earth is released through
geothermal activity. All of these
energy sources can be used by
humans.
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8a
Non-Renewable Energy
Non renewable energy is
energy that comes from the
ground and is able to be not
replaced within a useful period
of time. Fossil fuels are the
main category of non
renewable energy. Fossil fuels
include; coal, oil and natural
gas. These resources come
from animals and plants that
have died millions of years ago
and then decomposed to
create a useable source of
energy for humans.
Mined minerals such as
uranium used for nuclear
power are also non renewable
sources of energy.
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8a
Fossil Fuels - Coal
Coal was formed millions of years ago when plants fell into peat swamps and were
buried by heavy earth and rocks. Over millions of years, the weight of the rocks and heat
in the ground turned the plants into coal.
Most of the world’s coal was formed 300–350 million years ago during the
Carboniferous period that was warm and damp, ideal for plant growth. New Zealand
coals are much younger – they were made 30–70 million years ago and they are a less
energy rich fuel. Coal is mined either underground or in large open cast mines.
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8a
Fossil Fuels – Oil and Gas
Oil and gas were formed
many millions of years ago from
dead sea organisms falling to the sea floor
and being covered by sediment. Over time the
sediment that covered these dead creatures was
compressed
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and formed rock. The carbon and hydrogen atoms that used to be
part of the dead organisms bodies reformed into fuel – the liquid form called oil and the gas
form. Oil and gas are mined by drilling deep into the ground from oil rigs.
8b
The limits of fossil fuels and the unlimited energy of the sun
Fossil fuels are a limited resource. Extraction and mining can be expensive and can
damage the surrounding area. Carbon dioxide gas that is released upon burning the fuels
are contributing to the warming of the climate. Human society has a dependence on fossil
fuels for energy but needs to consider alternative renewable energy sources to replace
decreasing coal, gas and oil supply. Renewable energy is sustainable and in many cases
produces little or no harm to the environment. As new technology develops to collect the
energy it will become cheaper.
Fossil
fuels
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Renewable
energy
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8c
Hydroelectric energy
Hydroelectric power makes electricity by using the energy from falling water.
The water comes from big dams across rivers, and flows down great tubes to
drive electricity generators. New Zealand is fortunate to have many rivers, such
as the Waikato river, which are suitable to make use of this type of energy
source.
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8c
Wind energy
Wind power can drive a turbine
with a propeller and generate
electricity. Wind power is becoming
more popular in New Zealand and a
number of “farms” have been
created such as along the hills in
Manawatu and the new site
between Hamilton and Raglan.
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8c
Solar energy
Solar power can make electricity by
using panels called photovoltaic cells
which converts sunlight into direct
current electricity. An inverter changes
the direct current into alternating
current which can then be used by
households and industry to power
machines and appliances.
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8c
Biomass energy
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Biomass relies on the
photosynthetic ability of
plants to convert solar
energy into chemical
energy. The chemical
energy stored in plants is
then broken down by
enzymes and useful
bacteria into biofuels to
be used in machinery.
This type of fuel is
renewable as long as the
same amount of trees are
planted to replace those
cut down. The carbon
dioxide released when
burning the fuels will also
be reabsorbed by the
plants as they grow.
8c
Geothermal energy
Geothermal energy
can be used to heat
water pumped
underground into
hock rocks and the
steam created then
powers turbines to
create electricity.
Hot steam that
comes from
naturally occurring
vents can also be
used.
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9aEnergy efficiency – how sources of energy are transformed into useful
energy and wasted energy
When energy is transferred, some of the
energy turns into forms we don't want.
This energy is called wasted energy.
Wasted energy takes the form of heat and
sometimes sound or light.
During any energy transfer, some energy is
changed into heat.
The heat becomes spread out into the
environment.
This dispersed energy becomes increasingly
difficult to use in future energy transfers.
In the end, all energy is transferred into heat
and eventually lost out into space.
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Energy efficiency – how sources of energy are transformed into useful
energy and wasted energy
9a
Efficiency is a measure of how well an
energy user (i.e, bulb or appliance)
transfers energy into the form we want.
efficiency (%) = (useful energy out ÷
total energy in) x 100.
or
efficiency (%) = (useful power out ÷ total
power
in) x 100
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9b
Energy efficiency – comparing types of light bulbs
Incandescent
Compact Florescent
LED
Life Span
(average)
1,200 hours
8,000 hours
50,000 hours
Watts of
electricity used
(equivalent to 60
watt bulb).
60 watts
13-15 watts
6 - 8 watts
Each of these
types of bulbs
produces the
same amount of
useful energy
but require
different
amounts of
input energy
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Transformation losses and inefficient use increase the amount of energy
required
9d
A large amount of energy use in a
home is spent on heating. If a
home is poorly insulated (with
materials that do not conduct
heat) then the heat will easily
escape and more energy will be
required to maintain the
temperature to a suitable level.
Leaving lights on when not being
used, using standard
incandescent light bulbs instead
of the CFL or LED bulbs and
leaving appliances switched on at
the wall when not in use are all
inefficient uses of energy.
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9d
Reducing energy loss from our homes
It is important to reduce the loss of heat from our homes. This is done by
increasing the insulation of our homes using the methods shown in the
diagram below.
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9d
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9d
Becoming more energy efficient
OLD
Appliances for use around the
house are being designed to be
more energy efficient. This
means that they require less
input energy to produce the
same amount of useful energy
output. Less waste energy is
produced in the form of heat
and sound.
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NEW
Light bulbs
Televisions
70
Refrigerators
Energy can be transferred by conduction, convection or radiation
10a
Conduction
of heat along
a solid object
Methods
of heat
transfer
Convection
currents in
liquids or
gases
Radiation
of heat
waves from
hot objects
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Liquids and Gases transfer heat energy by Convection
10a
Convection occurs when free moving
particles found in liquids and gases
have heat energy added to them. This
causes an increase in kinetic energy of
the particles and as they collide into
each other they push apart more. The
hotter area of liquid or gas becomes
less dense or lighter and rises. As the
particles lose energy they slow down
and become closer to each other
which makes them denser and they
fall back down. This movement creates
convection currents where the
particles circulate.
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Hot air balloons rise due to Convection
10a
When you heat the air in the
balloon your increase the
kinetic energy of the air
particles. The air particles
absorb the heat energy and
move faster. This makes them
move faster. Air particles are
pushed out of the balloon, as
they take up more space.
A hot air balloon rises because
it is filled with hot, less dense
air and is surrounded by colder,
more dense air.
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10a
Solids transfer heat energy by Conduction
When heat is transferred by
conduction – the atoms remain in
fixed solid position – and the heat
energy is transferred from one atom
to another by being carried by
moving electrons surrounding the
atoms. The more heat energy an
electron has the faster it moves.
Some materials conduct better than
others. They are called conductors
and include metals which have
electrons that are free to move.
Those materials that cannot conduct
heat are known as insulators. They
have no free electrons to carry the
heat energy.
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10b
Vacuums transfer heat energy by Radiation
Radiation
source
Heat Energy can transferred in
waves – it does not need atoms or
electrons to travel. Our greatest
source of radiation waves comes
from the sun.
White and silver objects reflect
radiation and very little heat energy
is transferred to them. Black objects
absorb radiation and a large
proportion of the heat energy is
transferred to them.
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reflected
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absorbed
white
silver
black
Temp.
down
Temp.
same
Temp.
up
The method of heat transfer is linked to the state of matter
Heat
Transfer type
What
does it
travel in?
Does it
require
matter to
travel?
Description
example
convection
Liquid
And
gas
yes
Heat energy
contained by
particles that move
and carry it.
Hot air balloon
rising when
burner is going
conduction
solids
yes
Heat energy is
passed from
particle to particle.
A metal spoon
heating up in a
hot drink
Radiation
In a
vacuum
no
Heat energy
travelling in infrared waves at the
speed of light
Skin warming
up while sitting
in the sun
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The method of heat transfer is linked to the state of matter
Conduction passes the heat
energy from particle to particle
and occurs in solids when the
particles are fixed in place. This is
like the rugby players passing the
ball from one to another.
Convection requires
particles to move
around such as in
liquid and gas and
carry around the
heat energy like a
rugby player carrying
the ball and running.
Radiation does not
require particles to
move the heat energy.
This is like a rugby ball
kicked which then
moves by itself down
the field without any
players required.
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light
kinetic
heat
sound
transformations
geothermal
gravitational
potential
Active
energy
Law
Energy can not be
created or destroyed
it can only change
from one form into another
Energy efficiency=
Useful energy x 100
Energy used
Black
chemical
nuclear
magnetic
elastic
electrical
Heat
transfer
Hotter
conducters
absorb
White
silver
colder
expansion
particles
contraction
metals
Non-conducters
radiation reflect
Waves
electromagnetic
No
matter
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conduction
Plastics
Particles
Energy
Air
moves
(non solids)
solids
convection
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move
insulators
Liquids
And
gases
More
Surface
Area
More
Heat
loss