Jodrell Bank Discovery Centre
Big Science: Big Telescopes
www.jodrellbank.net
Gravity: Lesson Plans
A series of 2-3 lessons on the nature of gravity for Key Stage 3 pupils.
This lesson plan has been developed by the Jodrell Bank Discovery Centre as part of the Science and
Technology Facilities Council’s (STFC) Science and Society Large Award project Big Science: Big
Telescopes.
This lesson plan is free for teachers to download and share.
This lesson/series of lessons is designed to excite and inspire pupils by engaging them with examples
of the ‘Big Science’ carried out with the ‘Big Telescopes’ funded by STFC, whilst also teaching key
points from the KS3 2014 Science National Curriculum.
Some of the Big Telescopes with funding from STFC include the VLT (Very Large Telescope), ALMA
(Atacama Large Millimetre/sub-millimetre Array), e-MERLIN (the UK's facility for high resolution
radio astronomy observations), E-ELT (European Extremely Large Telescope) and SKA (Square
Kilometre Array).
The Lovell telescope at Jodrell Bank, part of e-MERLIN.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
www.jodrellbank.net
Table of Contents
Introduction ............................................................................................................................................ 3
Lesson Plan Part 1: Gravity on Earth ....................................................................................................... 4
Lesson Plan Part 2: Big Telescopes ......................................................................................................... 9
Lesson Plan Part 3: Gravity in Space ..................................................................................................... 13
Practical Activity 1 ................................................................................................................................. 17
Practical Activity 2 ................................................................................................................................. 19
Answers to the Mass and Weight Worksheet ...................................................................................... 21
Answers to the Part 1 Review ............................................................................................................... 22
Answers to the Part 3 Review ............................................................................................................... 22
Additional Resources ............................................................................................................................ 23
Use of Images ........................................................................................................................................ 23
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
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Introduction
Gravity is one of the four fundamental forces in the universe. The force of gravity was first described
mathematically by Sir Isaac Newton in 1687. His theory described how objects feeling the force of
gravity behaved, but Newton could not explain gravity’s origins. This came in 1916, when Albert
Einstein published his theory of General Relativity, which described gravity as the result of mass
curving space-time around it.
Through observations made by Big Telescopes, our understanding of gravity is tested. These
observations include examining how objects like planets and stars move in space and the way light
bends around massive objects like galaxies. This is still an open area of research as there are many
mysteries remaining in the universe. The answers to some of these mysteries may force us to update
our current ideas of gravity.
These lesson plans are presented in three sections: Gravity on Earth, Big Telescopes and Gravity in
Space. Depending on the length of lessons in your school these could be delivered as a single lesson,
or split into a series of two or three separate lessons.
Within this lesson/series of lessons your pupils will learn about the classical force of gravity, put
forward by Newton. They will learn the difference between mass and weight, the equation that
relates the two and perform an investigation into the strength of gravity on Earth. Pupils will then
use a 3D model of gravity, similar to the model of General Relativity put forward by Einstein, to
better imagine the force of gravity and its effects.
All pupil materials are provided, including suggestions on how these could be differentiated for
different abilities. At the end of sections one and three there are review questions that assess the
learning objectives of those sections.
An artist’s impression, using real data from the European VLT telescope, of the stars which orbit the supermassive blackhole at the centre of the Milky Way galaxy and the cloud of gas which is falling into it.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
www.jodrellbank.net
Part 1: Gravity on Earth
Learning Objectives
All
Most
Some







Comprehend the terms mass and weight
Use the formula weight = mass x gravity
Run a scientific investigation, taking repeat readings to collect meaningful results
Identify anomalous data to generate more accurate results
Compare everyday evidence with evidence from the Moon to conclude air resistance prevents objects falling at the same rate
Rearrange the formula weight = mass x gravity
Analyse data to conclude that objects fall at the same rate regardless of mass (depending on choice of practical activity)
Suggested timeline of activities (times dependent on group)
Time &
Activity
0-3 mins
Introduction
Activity details
Introduce topic,
structure of lesson
and lesson
objectives (if
required).
Slide
Teaching notes

1&2


Part 1 focuses on our experience of gravity on Earth and includes a
practical investigation to measure the strength of gravity on Earth.
Part 2 describes how Big Telescopes are used to collect data about
objects in space.
Part 3 uses a model to investigate how gravity behaves over large
distances between planets and stars.
Differentiation
N/A
Use the hyperlink on the slide to be taken to the official video on
YouTube.
3-8 mins
Part 1: Starter
Watch Felix
Baumgartner’s
record breaking
jump in 2012.
3
Felix Baumgartner is an Austrian skydiver. On 14th October 2012, he set
the world record for skydiving by falling from 39 kilometres (24 miles)
above the Earth’s surface. On his descent he reached an estimated
speed of 1,357.64 km/h (843.6 mph), or Mach 1.25. He became the
first person to break the sound barrier without vehicular power.
N/A
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Big Science: Big Telescopes
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8-10 mins
Introduce
Newton and
mass
Introduce Newton’s
theory of gravity and
set the lesson in
historical context.
4
Newton developed the first mathematical description of the force of
gravity. Newton said that he started thinking about gravity after
watching an apple fall from a tree (it did not actually hit him on the
head, as it is often claimed!). After much work he realised it was the
same force that was holding the Moon in orbit around the Earth. His
theory perfectly described the force between the Earth and Moon and
how they moved.
N/A
NB: Newton did not discover gravity; this is a common misconception.
He was the first to realise that gravity extended out into space; that it
was gravity which kept the Moon in orbit around the Earth and the
planets in orbit around the Sun. Previous to this, it was thought to
perhaps be a magnetic force.
Define the term
mass.
5
Newton realised that any object which has mass produces a force of
gravity and attracts other objects with mass. The size of that force
increase as the object’s mass increases.
N/A
Mass refers to the amount of matter an object is made from. Mass is
measured in grams and kilograms.
10-12 mins
Introduce
weight
Assess pupils' prior
knowledge of
weight.
6
Present pupils with the image of the dog (there is no reason for it to be
a dog, I just like dogs). Ask them to choose the force acting on the dog
(represented by a force arrow), and then name the force. Most pupils
would probably name the force as ‘gravity’. This answer would be
accepted in most KS3 tests; however the correct name for the force is
‘weight’. This activity requires pupils to have a prior knowledge of
representing forces with force arrows.
Pupils could vote on their choices
using voting cards, or miniwhiteboards. For higher
achieving pupils the options
could be deleted and pupils could
draw their answer on the board,
if using an IWB. Alternatively side
6 could be printed out for pupils,
to answer individually or in
pairs/groups.
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Big Science: Big Telescopes
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12-14 mins
Summary
14-20 mins
Questions
20-32 mins
Practical
activity 1
Summarise the
difference between
the terms mass and
weight.
Assess pupils
understanding of
mass and weight, by
using the equation.
Practical
investigation
measuring the
strength of gravity
on Earth.
7
Summarise the difference between the terms mass and weight using
the table and introduce the equation which relates the two.
Some pupils often struggle to understand ‘mass’ and the difference
from ‘weight’, since the terms are used in everyday life
interchangeably.
Peer support could be used for
pupils who are struggling. Pupils
could be asked to consider
situations where weight would
be different, but mass the same.
N/A
See the accompanying document ‘Mass and Weight Worksheet’. The
questions require pupils to use the formula W=mg. The Earth is not
used as an example on this worksheet, since measuring the strength of
gravity on Earth is the objective of the following practical activity. For
the answers go to Answers to the Mass and Weight worksheet.
The questions supplied become
gradually harder. Select and use
the questions suitable for your
group.
8
See section Practical activity 1 for more information about the various
practical activities available at this point.
Pupils could be placed in mixed
ability groups, for peer support.
Alternatively, different groups
could complete different
experiments based on their
achievement. Pupils could then
compare to see if different
methods gave the same results.
9
Depending on which practical activity your pupils have followed, they
may need to identify and delete anomalous readings. This will be
especially important if they have completed a data logging or freefall
timing activity.
Pupils could decide within groups
which are the anomalous
readings. Alternatively pupils
could take copies of the results
and analyse them individually.
32-36 mins
Determine
anomalous
readings
Pupils identify and
delete anomalous
readings.
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Big Science: Big Telescopes
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36-40 mins
Reflect on
practical
Pupils bring together their results, to form a class average. The first
three questions on slide 10 provide pupils with a structure to evaluate
their results and their methodology.
Pupils review their
findings and
methodology.
10
If pupils concluded that freefall acceleration is independent of mass in
the above practical, this can be linked to the activity below.
40-42 mins
Consider a
popular
misconception:
that heavy
objects fall
quicker than
lighter objects
The fourth question has been specifically included if you have
completed a freefall practical and have used differing masses of
similar sizes. In this case, acceleration results should be independent
of mass (depending on quality of results) and some pupils may be able
to discern this.
If you have completed a freefall
practical and used differing
masses of similar sizes, some
higher achieving pupils may be
able to recognise that
acceleration of fall is independent
of mass (depending on the quality
of pupils’ results).
Test prior
knowledge of
misconception.
11
Ask pupils to consider a hammer and a feather. Which one has the
largest weight force? Which one will hit the ground first when
dropped?
Why?
The hammer will have the largest weight (shown by the larger force
arrow). On Earth, the hammer will fall to the ground quickest, but this
is not because it is heavier.
Pupils could vote on the correct
answer, maybe using voting
cards, or mini-whiteboards.
Higher achieving pupils could be
asked to explain why the hammer
falls to Earth quicker, to better
assess prior knowledge.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
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In 1971, during the Apollo 15 mission on the Moon, Commander David
Scott dropped a 1.3 kilogram hammer and a 3 gram feather from the
same height.
42-46 mins
Address
misconception
that heavy
objects fall
quicker than
lighter objects
46-50 mins
Review of Part
1
1
Show evidence
contradicting
misconception.
12
Click the link to watch this video on YouTube. The quality is not great due
to the 1970s recording technology. Hopefully it can be seen that both
objects hit the Moon’s surface at the same time.
It’s possible to complete this as a demonstration in the classroom, with a
‘guinea and feather tube’ and a vacuum pump1.
Ask pupils to re-evaluate everyday experience, with new understanding.
Pupils re-examine
evidence based
on new
knowledge.
Assess whether
learning
objectives have
been met.
13
14
The only reason that a feather falls slower than a hammer on the Earth is
that air resistance has much more of an effect on the feather. The Moon
on the other hand is a vacuum. Since it has no atmosphere, there is no air
resistance slowing the feather’s descent.
To assess the learning objectives of part 1, pupils can answer the six
questions presented on slide 14.
See Answers to the Part 1 Review for the answers.
An example of this experiment being done can be found at https://www.youtube.com/watch?v=clom4DdnFfM
Pupils could be asked to predict
what will happen. Higher
achieving pupils could be asked to
rationalise their choice, lower
achieving pupils could vote on a
number of multiple choice
options.
Some pupils may be able to
answer this question directly.
Others may require further
support, such as a list of
differences between the Moon
and Earth. Pupils could answer in
groups, or think-pair-share.
Pupils could peer assess their
answers and suggest
improvements where necessary.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
www.jodrellbank.net
Part 2: Big Telescopes
Learning Objectives
All
Most
Some





Set 'Part 3: Gravity in Space' in a real-world, global context
Understand that science is ongoing and new scientific projects are underway
Inspire pupils with the scale and scope of scientific enquiry
Comprehend that visible light is not the only sort of wave that travels through space and that other waves show different things
List the advantages of building big telescopes
Suggested timeline of activities (times dependent on group)
Time & Activity
0-2 mins
Introduce Part 2
2-4 mins
Current gravity
research
2
Activity details
Introduce idea that
astronomers need
to collect data.
Introduce learning
objectives if
required.
Introduce concept
that science
research is ongoing
and there is still a
lot we don’t know.
Slide
15
Teaching notes
In order for astronomers to study gravity in space, they need to make observations
of planets and stars with telescopes.
Differentiation
N/A
But why do astronomers need to study gravity?
There is still a lot we don’t know about gravity in space. For example, we don’t
know if our current theories of gravity are completely correct, or what happens
when gravity is very strong, or very weak2.
16
N/A
Looking at the effects of gravity can also tell us about the universe and help us
answer questions, such as, “What is Dark Matter?” We need telescopes to look
into space to answer these questions (and many more!).
Seven mysteries about gravity: http://www.newscientist.com/special/seven-things-that-dont-make-sense-about-gravity
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Big Science: Big Telescopes
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Telescopes can be thought of as giant eyes which have been built to collect more
light and see objects better.
This is the VLT (Very Large Telescope) and a picture of the Sombrero Galaxy taken
by it.
4-6 mins
Telescope
example
Introduce VLT
(Very Large
Telescope) as
example of current
big telescope.
17
It is owned and run by ESO (the European Southern Observatory). There are 15
countries involved in ESO, including the UK. The VLT is made up of 4 telescopes,
each 8 m across. Each telescope uses a curved mirror to collect light and focus it on
to a detector. The 4 telescopes can work individually or all together to boost their
seeing power.
The VLT is 2.6 km high, on a mountain in Chile where the air is very thin. This
means it has an extremely clear view of the sky. It also uses a laser to measure
distortions in the air (this is called Adaptive Optics). This means it can take even
better quality images3.
3
4
More information on the VLT can be found here: http://www.eso.org/public/teles-instr/vlt/
A list of the ten biggest telescopes in the world can be found here: http://www.space.com/14075-10-biggest-telescopes-earth-comparison.html
For higher achieving
pupils, this could be
extended into a
research task. Pupils
could look up this
and/or other big
telescopes around the
world and present
their findings to the
rest of the class4.
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Big Science: Big Telescopes
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Light is a form of (electro-magnetic) radiation, but there are many others.
Astronomers don’t just use telescopes that look at light, they also use telescopes
designed to pick up these other forms of radiation.
6-7 mins
Astronomy at
other
wavelengths
Introduce
telescopes that
observe other
forms of (electromagnetic)
radiation.
Here are three examples: The SOHO (SOlar and Heliospheric Observatory) satellite
a joint mission by the European Space Agency and NASA. Launched in 1995, SOHO
observes the Sun in light and ultra-violet rays. SOHO is orbiting in space 1.5 million
kilometres from Earth5.
18
NASA’s James Webb space telescope is due for launch in 2018. It will observe cool
objects in the universe by detecting infrared radiation. It will look for the first
galaxies after the Big Bang and see how stars and planets form in massive clouds of
gas and dust6.
The Lovell telescope at Jodrell Bank in Cheshire is part of the University of
Manchester. It was built between 1952 and 1957 and it picks up radio waves from
objects like exploding stars, dead stars and galaxies out in space. Its dish is 76
metres across, which makes it the third largest steerable telescope in the world7.
7-8 mins
Example of
observations
5
Example of an
observation in
another form of
radiation.
This content links in to
most Key Stage 4
specifications on the
electro-magnetic
spectrum.
This is an image of the Sun as it appears to our eyes, in visible light (warning: never
look directly at the Sun!).
19
By looking with ultra-violet rays however, we can see many more features that we
couldn’t before. This image was taken by the SOHO satellite. By looking with other
forms of radiation, astronomers see things that would be completely invisible in
ordinary light. Other forms of radiation reveal a hidden universe!
More on SOHO at: http://sohowww.nascom.nasa.gov/
More on James Webb Space Telescope here: http://jwst.nasa.gov/index.html
7
More on the Lovell telescope at: http://www.jb.man.ac.uk/aboutus/lovell/
6
Some pupils may be
familiar with some
other forms of
radiation, especially
infrared radiation
(which can be felt as
heat). This is the same
radiation that is
picked up by heat and
night vision cameras.
N/A
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Big Science: Big Telescopes
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Right now scientists and engineers around the world are building new, bigger and
better telescopes. Big telescopes see better than smaller ones, but why?
8-9 mins
Advantages of
big telescopes
List the advantages
of big telescopes.
20
Firstly, big telescopes collect more light, so can see fainter objects (like eyes
widening in the dark).
Big telescopes also create better quality (sharper) images8.
Some pupils may be
able to predict that
big telescopes can
collect more light,
especially if prompted
to consider the eye as
an analogy. Pupils
could think-pair-share
their ideas.
With modern technology (e.g. supercomputers and fibre-optic data networks) it is
preferable to build many linked smaller telescopes, rather than single large ones.
9-10 mins
Example of
future
telescope
Example of a
future science and
engineering
development.
21
The Square Kilometre Array (SKA) will be the largest radio telescope in the world,
built of over 3000 smaller dishes, spread across the deserts of Australia and South
Africa9. It will act like one giant telescope thousands of kilometres wide. A
telescope that size would be impossible to build as one giant dish! The SKA will be
so powerful it will be able to detect organic molecules in space.
N/A
The SKA is being built by a global partnership of ten countries: Australia, Canada,
China, Germany, Italy, New Zealand, South Africa, Sweden, the Netherlands and
the United Kingdom (India is also an Associate Member).
8
9
The explanation for this is A-level physics, so it is not addressed here, but it can be found at http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp.html
More information on SKA can be found at http://www.skatelescope.org/
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Big Science: Big Telescopes
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Part 3: Gravity in Space
Learning Objectives
All
Most
Some



To comprehend the terms star, galaxy and universe
Use a 3D model of gravity to address the misconception that there is no gravity in space
Evaluate a 3D model of gravity
Suggested timeline of activities (times dependent on group)
Time & Activity
Activity details
Slide
Teaching notes
Differentiation
Now we will consider how gravity acts on larger scales; not only on
the surfaces of planets, but further out. Gravity affects how all
objects in space move, such as planets and stars.
0-3 mins
Introduce Part
3
Introduce gravity
on a larger scale.
22
As a starter: Pupils could guess what the picture on slide 22 shows.
Pupils could write their guesses on mini-whiteboards or post-it
notes.
The image shows an artist’s impression, using real data from the
European VLT telescope, of the stars which orbit the supermassive
black-hole at the centre of our Milky Way galaxy and the cloud of
gas which is falling into it. It’s the force of gravity from the blackhole that is causing all this to happen.
Some pupils may not yet be familiar
with the term galaxy.
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Ask pupils which arrow correctly represents the force of gravity
acting on the astronaut.
3-5 mins
Assess prior
knowledge
5-15 mins
Practical
activity 2
Assess pupils'
understanding of
23
the direction of the
force of gravity.
Introduce practical
activity.
Pupils use a 3D
model of gravity.
24
25
15-17 mins
Identify
examples in
space where
gravity acts
Gravity will act between the centre of the astronaut and the centre
of the Earth. Technically, gravity will act equally in both directions,
but the effect of the force on the Earth from the astronaut is
negligible (since the Earth is so massive) and so it can be ignored.
The astronaut will be pulled towards the centre of the Earth.
See section Practical activity 2 for more information about the
practical activity available at this point.
High achieving pupils could be asked
to design and construct their own
models of gravity.
Slide 25 lists some examples of questions pupils could investigate
using the equipment.
Question 5 (what are the similarities
and differences between this model
and real life?) is aimed at high
achieving pupils (see Practical
activity 2 for more information).
Gravity keeps satellites in orbit around the Earth.
Example 1:
Satellites
26
Pupils could vote on their choices
using voting cards, or miniwhiteboards. For higher achieving
pupils the options could be deleted
and pupils could draw their answer
on the board, if using an IWB.
Alternatively side 23 could be printed
out for pupils, to answer individually
or in pairs/groups.
A ball tethered to a piece of string and whirled overhead can be
used to represent an orbit. The tension in the string represents the
tug of gravity; preventing the ball/satellite from hurtling off into
space.
High achieving pupils could be asked
to come up with a list of examples
before being presented with slides
26-28.
Other examples could include;
keeping Moons in orbit around
planets, the pull of black holes,
galaxies interacting with each other,
and so on.
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In exactly the same way, gravity keeps planets in orbit around the
stars.
Example 2: planets
27
17-21 mins
N/A
Stars are grouped together in space in galaxies. On average a galaxy
contains about 100 billion stars. Stars are held together in galaxies
by the force of gravity between them.
Identify further
examples in
space where
gravity acts
Define terms
star and galaxy
It is a common misconception that gravity drives the motion of the
planets around the Sun. This is not the case. There is no force
driving the planets around the Sun; the planets were formed in
motion and there are no resistance forces in space to slow them
down.
Example 3:
Galaxies
28
This is a picture of galaxy NGC1300, taken by the Hubble Space
Telescope. It is a barred spiral galaxy with two spiral arms (barred
refers to the straight 'bar' of stars that runs through the central
bulge of the galaxy). This is the same type of galaxy that we think
our Milky Way galaxy is. We cannot take an image of our own
galaxy like this, since we are inside it. Our Milky Way galaxy
contains around 200 billion stars.
A popular analogy is that a galaxy is like a 'city' of stars; the stars
being the individual houses in that city.
N/A
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21-24 mins
Define term
universe
Consider image of
Hubble Deep Field.
28
This is an image called the Hubble Ultra Deep Field, taken by the
Hubble Space Telescope. The Hubble Space Telescope was pointed
out into deep space to take this image. The image is of a tiny patch
of sky, in which we can see almost to the edge of the observable
universe. The image shows many galaxies, separated by vast
distances of empty space. It is estimated that there are around 100
billion stars in the observable universe.
The term universe refers to everything; all the matter and energy in
existence.
24-30 mins
Review of Part
3
Assess whether
learning objectives
have been met.
29
To assess the learning objectives of part 3, pupils can answer the
eight questions presented on slide 29.
See Answers to the Part 3 Review for the answers.
Higher achieving pupils could
estimate the number of stars in the
observable universe; 100 billion stars
per galaxy x 100 billion galaxies =
1024 stars. This number is larger than
the total number of grains of sand on
all the beaches of the Earth!
Higher achieving pupils could be
asked to review the 3D model of
gravity used. That is: in what ways
did the model successfully simulate
the force of gravity? In what ways did
it fail? How could the model be
improved?
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Practical activity 1
Objective: To measure the strength of gravity on the Earth's surface.
Option 1: Freefall (Data logging)
The strength of gravity is also defined as the 'acceleration due to gravity'. Therefore it is possible to
directly measure the strength of gravity by measuring the acceleration of an object as it drops to the
ground. For an experiment of this nature, we recommend a group size of three or four.
If you choose to run a freefall experiment, you may need to consider the following:




You will probably need to use data logging equipment which uses one or two light-gates.
Choose suitable objects to drop; smaller, denser objects work best as they are less affected by
air resistance. Also, if using data logging equipment, the objects may need to be a regular size;
e.g. square. Please check what your data logging software recommends.
Data logging software will usually enable your pupils to collect a high number of results.
However, many of these results may be highly inaccurate, e.g. if the dropped object only falls
through one light gate and misses the second, or falls at an awkward angle. To enable pupils to
record successful and unsuccessful readings, we have provided a “Data validity worksheet”. By
referring to this record when analysing their results, pupils can remove their unsuccessful
readings from the calculation of their average.
It may be possible to demonstrate that acceleration due to gravity is independent of the weight
of the object being dropped (i.e. heavy objects do not fall quicker than light objects). This
depends on pupils collecting good quality results in terms of accuracy. Provide pupils with a
variety of objects of different weights, but similar sizes (exactly the same size if possible). For
example, small blocks made out of wood or metal. Provided the lightest objects are not so light
that they are greatly affected by air resistance, there should not be a correlation between
weight and acceleration.
Depending on the equipment available in your school, it is possible to run a freefall experiment with
one or two light-gates. See more information on these options below.
A. Using data logging equipment with two connected light-gates
Equipment needed
Computer/laptop running data logging software
A pair of connected light-gates
Clamp-stand
Regular shaped object to drop
The easiest way to complete a free-fall experiment is with data logging equipment that uses two
connected light-gates. Attach the light-gates to a clamp stand, one on top of the other, and then
drop an object through the light gates, making sure the object breaks the beams of both light gates.
Most data logging software will directly calculate the acceleration of the object, provided the size of
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the object and the distance between the light-gates is known. Please refer to your data logging
software instructions on how to do this. Pupils can then copy their results to an Excel spreadsheet,
where they can delete unsuccessful readings and/or anomalous data before calculating their
average.
B. Using data logging equipment with a single light gate
If you do not have access to connected pairs of light-gates, another option is to use a single lightgate and a stopwatch.
Equipment needed
Computer/laptop running data logging software
A light-gate
Clamp-stand
Stopwatch
Regular shaped object to drop
Drop an object from a suitable height above the light-gate. Time on a stopwatch how long it takes
from the start of the drop, to the object passing through the light-gate. The height of the drop does
not need to be known. The light-gate should be used to take a measurement of the final speed of
the object. Most data logging software will directly calculate the speed, provided the size of the
object is known. The acceleration can then be calculated from the equation acceleration = (final
speed - initial speed) ÷ time. Since the initial speed = zero (provided the object is dropped, not
thrown), this simplifies to acceleration = final speed ÷ time. Pupils could enter their results into an
Excel spreadsheet which calculates the acceleration for them, using this equation. Pupils can also
delete unsuccessful readings and/or anomalous data before calculating their average.
Option 2: Newton meters
If light-gates and data loggers are not available to you, pupils can measure the strength of gravity on
Earth by taking measurements from masses hanging from Newton meters.
Equipment needed
Newton meter
Variety of masses
By hanging different masses from Newton meters and reading off the weight, it is possible to
calculate the strength of gravity in N/Kg, from the equation strength of gravity = weight ÷ mass.
Pupils may get a variety of readings from different Newton meters and also if the masses attached
are too low to stretch the spring, or so large that they overstretch the spring. This will give pupils the
opportunity to identify anomalous results and to calculate a class average. For a Newton meter
experiment, we recommend a group size of two.
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Practical Activity 2
Objective: To use a 3D model of gravity to address the misconception that there is no gravity in
space.
Method
Equipment needed
Hula hoop
Approx 1m2 (depends on size of hula hoop) of stretchy lycra material
Bulldog clips
Balls of different sizes and masses
Cut a section of stretchy lycra material so that it can be stretched taut over a hula hoop and securely
clip it with bulldog clips around the edge. This is now a 2D representation of space. Hold up the hula
hoop above the ground and place a ball on the lycra surface. A suitably heavy ball will sink into the
lycra, creating a curve. The ball represents a star or planet in space and the curved lycra represents
the gravity field around it.
Pupils should draw an analogy between the stretched lycra and an object’s gravity extending
outwards into space, gradually getting weaker as the distance increases. This will hopefully work
towards dispelling the misconception that gravity is binary, i.e. that is that it is ‘on’ at the surface of
the Earth and ‘off’ when in space.
This model actually represents the curved ‘spacetime’ of Einstein's theory of General Relativity,
published in 1916. In this theory, Einstein proposed that mass bends spacetime around it, curving
and stretching space and time (opposed to the perfectly flat space in classical physics). Objects, e.g.
planets or particles or rays of light, travelling near massive objects such as stars and other planets
follow the curvature of space, so their path bends around these objects. We perceive this change of
direction as the force of gravity pulling on them.
For this activity, we recommend a group size of three or four. An excellent (if very large scale!)
demonstration of this activity can be found at: https://www.youtube.com/watch?v=MTY1Kje0yLg.
Examples of things to try
These are listed on slide 25 of the accompanying PowerPoint, but more information is found below.
1. Place a second ball onto the lycra. The two balls will be attracted together, if they come too
close to one another.
2. Experiment with the strength of the 'gravity fields' around balls of different masses.
3. Try to get a planet (a smaller, lighter ball, e.g. a marble) to orbit around a star (a larger,
heavier ball).
a) By rolling the planet around the star. It’s possible to get one or two good orbits, but not
many more; the planet will lose energy quickly and start spiralling into the star, due to
the friction of the fabric (there is no friction in space, so this does not occur).
b) By applying small rotations. First, apply a bit of pressure to the star to hold it in place.
Now those holding the hula hoop can rotate it in small circles. This will provide the force
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necessary to overcome the friction of the lycra and start the planet rolling around (in
real space there is no friction, so no constant driving force is required). The gravity of the
star will constrain the planet and keep it in orbit. If the driving force is too strong, the
planet will overcome gravity and fly off out into space.
4. Try to get a planet to orbit two stars in a figure of eight shape (you may have to hold the
stars in place to stop them attracting together). Many stars exist in binary systems. A figure
of eight also represents the path the Apollo missions took to get to and from the Moon.
5. Consider the similarities and differences of this model with real life (for higher achieving
pupils). This model excellently demonstrates the pull of gravity in one plane, however in
reality gravity acts in three dimensions. Also this model has a lot of friction, so objects lose
energy quickly.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
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Answers to the Mass and Weight worksheet
1. How much would a 10 Kg suitcase weigh on the surface of…?
a. The Moon
16 N
b. Mars
37 N
c. Saturn
90 N
d. Pluto
6N
2. How much would a 25 Kg suitcase weigh on the surface of…?
a. Mercury
95 N
b. Venus
220 N
c. Jupiter
577.5 N
d. Uranus
217.5 N
3. What would be the mass of a 10 Kg suitcase be on…?
a. Mercury
10 Kg
b. Venus
10 Kg
c. Neptune
10 Kg
4. Which place in the above table will it be easiest to stand up? Why? Pluto, gravity is weakest
5. On which place from the table above would you have…?
a. The most weight
Jupiter
b. The most mass
N/A: mass would be the same on every one
6. If you stood on Mars and had to pick up a 15 Kg pack, you would have to pull with a force
greater than…?
55.5 N (this is the force of weight on the pack)
7. If a 60 Kg person was standing on a platform at the surface of Saturn and they jumped, they
would have to push with a force greater than…?
540 N (this is the force of weight on the person)
8. The Curiosity rover on Mars has a weight on Mars of 3,330 N. What is its mass?
mass = weight/g = 3330/3.7 = 900 Kg
9. A 60 Kg person standing on the dwarf planet Ceres would weigh 16.2 N. What is the strength
of gravity on the surface of Ceres?
g = weight/mass = 0.27 N/Kg
10. Jupiter is made of gas (like Saturn, Uranus and Neptune). What would happen to the
strength of gravity if you...?
a. Moved away from Jupiter
It would get weaker
b. Fell in to Jupiter
It would get stronger
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Answers to the Part 1 Review
1. What is mass and what is it measured in?
Mass is a measure of the amount of matter that an object is made of.
It is measured in Kilograms.
2. What is weight and what is it measured in?
Weight is the amount of force acting on an object with mass, due to gravity.
It is measured in Newtons.
3. Write down the equation that relates mass and weight.
Weight = Mass x gravity
4. What is an anomalous result and why should you ignore it?
An anomalous result is one that is very obviously different from other measurements, due
to some error in the experiment. It should be ignored to give more accurate results.
For questions 5 and 6, imagine both objects being dropped at the same time and from the same
height.
5. A bowling ball and a leaf.
a) Which object would land first on the Earth? Bowling ball
b) Which object would land first on the Moon? Both would land at the same time
c) Which object weighs more? Bowling ball
6. A piece of paper scrunched up into a ball and an identical, but flat piece of paper.
a) Which object would land first on the Earth? Scrunched up paper
b) Which object would land first on the Moon? Both would land at the same time
c) Which object weighs more? Both weigh the same
Answers to the Part 3 Review
1. Place these objects in order from smallest to largest: Galaxy, universe, planet, star.
Planet, star, galaxy, universe
Decide whether the statements are true or false. If the statement is false, write a correct statement.
2. The Earth’s gravity pulls objects downwards, towards the South pole.
FALSE. Gravity pulls objects towards the centre.
3. There is no gravity in space.
FALSE. Gravity extends outwards into space from objects.
4. The more mass an object has, the stronger its force of gravity. TRUE.
5. A planet’s gravity pulls objects towards the centre of that planet.. TRUE.
6. The force of gravity extends outwards from objects. TRUE.
7. Gravity sometimes pushes objects apart.
FALSE. Gravity only attracts objects together.
8. The force of gravity from an object stays the same no matter how far away you are from the
object.
FALSE. The force of gravity gets weaker the further you go from an object.
Jodrell Bank Discovery Centre
Big Science: Big Telescopes
www.jodrellbank.net
Additional resources on big telescopes
1. Full 50 minute documentary about current big optical telescopes
http://www.youtube.com/watch?v=QeobrudynUE
2. Square Kilometre Array Official Animations http://www.skatelescope.org/mediaoutreach/videos/
3. More information about current and future big telescopes, including school resources
http://www.bigtelescopes.org.uk/
4. Star Gazing Live video demonstrating how to make your own small telescope
http://www.bbc.co.uk/programmes/p00n6zkf
Use of Images
All images used in this lesson's presentation have been released under a creative commons license.
Every effort has been made to credit all images used. Where images do not display credits, this is
because this information could not be found. If you believe an image has been used incorrectly or
has been mis-credited, please email Jamie Sloan on the address shown below and we will be happy
to amend the presentation.
jamie.sloan@manchester.ac.uk