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9J Gravity and Space
Mass and weight
• What is gravity?
• What is weight? What units is it measured
in?
• What is mass? What units is it measured in?
• How could you change your weight?
• How could you change your mass?
True or false?
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If the earth stopped spinning we would float into space.
There is no gravity on the moon.
NASA have an anti-gravity room where gravity can be turned off
and people can float.
It is possible to shield the force of gravity by using lead or other
materials.
Isaac Newton discovered gravity.
Nottingham Forest football team won the Champions league in 1979
and 1980.
You have no mass in space.
There is no gravity in space because you are far from the earth.
Weight is measured in kilograms.
There is no gravity in space because space is a vacuum.
If we could suck all the air out of the classroom, we would float
around.
All false!
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Only this one is
true!
If the earth stopped spinning we would float into space.
There is no gravity on the moon.
NASA have an anti-gravity room where gravity can be turned off
and people can float.
It is possible to shield the force of gravity by using lead or other
materials.
Isaac Newton discovered gravity.
Nottingham Forest won the Champions league in 1979 and 1980.
You have no mass in space.
There is no gravity in space because you are far from the earth.
Weight is measured in kilograms.
There is no gravity in space because space is a vacuum.
If we could suck all the air out of the classroom, we would float
around.
Gravity
What is gravity?
Gravity
Gravity is a force between ALL objects!
Gravity
Gravity
Gravity is a very weak force.
The force of gravitational attraction between Mr
Porter and his wife (when 1 metre apart) is only
around 0.0000004 Newtons!
Gravity
The size of the force depends on the mass of
the objects. The bigger they are, the bigger
the force!
Small attractive force
Bigger attractive force
Gravity
The size of the force also depends on the
distance between the objects.
Gravity
We only really notice the gravitational
attraction to big objects!
Hola! ¿Como estás?
Gravity
The force of gravity on something is called
its weight. Because it is a force it is
measured in Newtons.
Weight
Gravity
On the earth, Ms Stamp’s weight is around
700 N.
I love
physics!
700 N
Gravity
On the moon, her weight is around 110 N.
Why?
110 N
Astronauts on the moon
Gravity
In deep space, far away from any planets or
stars her weight is almost zero. (She is
weightless). Why?
Cool!
Mass
Mass is a measure of the amount of material
an object is made of. It is measured in
kilograms.
Mass
Ms Stamp has a mass of around 67 kg. This
means he is made of 67 kg of blood, bones,
hair and poo!
67kg
Mass
On the moon, Ms Stamp hasn’t changed
(she’s still Ms Stamp!). That means she still
is made of 67 kg of blood, bones, hair and
poo!
67kg
Gravity
In deep space, Ms Stamp still hasn’t
changed (she’s still Ms Stamp!). That
means she still is made of 77 kg of blood,
bones, hair and poo!
I feel sick!
67kg
Mass and weight
Mass is a measure of the amount of material
an object is made of. It is measured in
kilograms.
Weight is the force of gravity on an object.
It is measured in Newtons.
Weight and Mass Experiment
• You are going to investigate the relationship
between mass and weight.
• Aim:
• Prediction:
• Variables: (independent, dependent,
control)
Mass (g)
Mass (kg)
Weight (N)
Calculating weight
• How do you calculate weight?
• What is the gravitational field strength on
The Earth?
Calculating weight
The force of gravity on one kilogram is
called the gravitational field strength. It s
measured in Newtons per kilogram (N/kg)
Calculating weight
To calculate the weight of an object you
multiply the object’s mass by the gravitational
field strength wherever you are.
Weight (N) = mass (kg) x gravitational field strength (N/kg)
Example
The gravitational field strength on earth is
around 10 N/kg. What is your weight if your
mass is 45 kg?
Weight (N) = mass (kg) x gravitational field strength (N/kg)
Weight (N) = 45 kg
x 10 N/kg
Weight = 450 N
The Universe
• Name the main objects in our solar system
• What is the name of our galaxy?
• How do we measure distances in space?
Put the cards in order of size
Our solar system
Moons in the solar system
Distances between the planets to
scale
http://www.northernstars.com/solar_system_distance_scal.htm
Our place in the universe
Satellites
• What is a satellite?
• Name a natural satellite of The Earth.
• Name a natural satellite of The Sun.
• Name an artificial satellite of The Earth.
Video
http://lgfl.skoool.co.uk/content/keystage3/Phy
sics/pc/learningsteps/STLLC/launch.html
Artificial Satellites
• What do we use artificial satellites for?
Artificial satellites
• Among other jobs, artificial satellites
orbiting the Earth are used for:
– telecommunications (transmitting
information between distant parts of the
Earth)
– satellite navigation systems (‘satnav’)
– spying on other countries, and
– weather forecasts.
Weather
• A weather satellite is primarily used to monitor
the weather and climate of Earth.
• Satellites can be either polar orbiting, seeing the
same swath of the Earth every 12 hours
• Or geostationary, hovering over the same spot on
Earth by orbiting over the equator while moving at
the speed of the Earth's rotation
Spying
• A spy satellite or reconnaissance satellite
observes the Earth
• They can also be used to listen to
communications and are deployed for
military or intelligence applications.
Sat Nav
• The Global Positioning System (GPS) is a spacebased system that provides reliable location
information in all weathers and at all times
• In car sat nav systems receive data from up to four
satellites giving accurate positioning
• Can be used anywhere on or near the Earth when
there is an unobstructed line of sight to four or more
GPS satellites.
Telecommunications
• Communications satellites occupy a geostationary
orbit.
• They are in orbit above the equator at just the right
distance so that it takes them one day to complete an
orbit.
• As a result, they always appear in the same position
when seen from the ground.
• This is why satellite television dishes can be bolted
into position and do not need to move.
Satellite orbits
• http://youtu.be/E4k3kEA3pmo
Using satellites to view
space
Astronomical satellites, such as the Hubble Space Telescope (HST),
are large telescopes placed in a high orbit far from the effects of the
Earth’s atmosphere.
These satellites can ‘see’
much further into space
and give us images of
stars and galaxies many
light years away, like
this cartwheel galaxy.