Concept activities
Inclined Planes
pages 37 - 43
1a: Ramp it up
1b: Thin end of the wedge (Teacher led demonstration)
1c: The turn of the screw (Teacher notes)
1c: The turn of the screw (Student worksheet)
Wheels
pages 44 - 45
2a: Wonderful wheels
2b: Wheels and axles at work
Levers
pages 46 - 51
3a: The law of the see saw (Teacher led demonstration)
3b: Lifting the load
3c: Location, location, location!
3c: Location, location, location! (Student worksheet)
3d: Lever launch
Pulleys
pages 52 - 53
4a: The power of pulleys
4b: Pulley tug of war (Teacher led demonstration)
Gears
pages 54 - 66
5a: Getting into gear (Teacher led demonstration)
5b: Gears in action (Teacher notes)
5b: Gears in action (Student worksheets)
5c: Egg-cellent gears! (Teacher notes)
5d: Gears: wheely good fun! (Student worksheet)
Pistons
pages 67 - 69
6a: Pumping pistons (Teacher notes)
6b: Pumping pistons (Student worksheet)
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Activity 1a: Ramp it up
Summary:
A simple demonstration of how ramps reduce the effort required to lift a load. The ‘force-distance
trade off’ is illustrated, and the effects of friction and different ramp angles can be investigated.
This activity can be done by measuring with a force meter or simply observing the stretch in a
rubber band or spring. Alternatively, a playground slide could be used as the ramp, with students
pulling on a heavier load for a more physical learning experience.
Aim:
To investigate how inclined planes can be used as simple machines.
What you need:
1 plank or wide board
1 large book
Rubber band (or Force meter)
1 chair
String
Short pieces of dowel or tubing (optional)
What to do:
1. Set up the ramp by resting the end of the board level with the seat of the chair.
2. Tie the string around the book. Attach the rubber band or force meter.
3. Consider: You need to shift this load up to the top of the chair. Should you pull it straight up off
the ground, or pull it up the ramp? Which will be easier to do? Will it make any difference at
all? After all, the load itself does not change! Discuss it with a partner.
4. Pull the book vertically straight up to the seat of the chair and measure the force, or the length
the rubber band has stretched.
5. Now pull it slowly up the ramp, and measure the force/stretch again.
6. Place the pieces of dowel or tubing under the book so the book rolls over them as you pull it
up. What effect does this have on your force measurement?
Discussion:
Even though it is not a very ‘high-tech’ piece of equipment, the plank has acted as a machine,
because it has made the job easier to do (it has reduced the effort force required). However, the
distance up the ramp is much less than the vertical distance - the ‘trade-off’ for using less pulling
force is that you have to pull further. Using rollers under the load reduces the friction between the
load and the ramp and lowers the force needed even more.
Extension:
The amount of work done lifting the load straight up and using the ramp can be calculated and
compared using the formula work = force (in newtons) x distance (m).
You will find that the work done pulling the load up the ramp is slightly larger. This is because extra
force must be applied to overcome the friction between the load and the ramp. Placing rollers
under the load reduces the amount of friction. Further investigation could be made into the effect
on the force of changing the angle of the ramp.
Cross-Curricular Link:
Investigate how ramps and rollers may have been used to build the pyramids or Stonehenge.
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Activity 1b: Thin end of the wedge
Teacher led demonstration
Summary:
Several demonstrations of how a wedge is used can be done with some student participation. If it
can be done safely at school, students could observe an axe being sharpened and/or used to chop
a block of wood.
Aim:
To use examples of wedges to demonstrate how they reduce the required input force and
transform a vertical force into a horizontal one.
What you need:
2 rectangular blocks of wood or polystyrene (but still small enough for students to hold)
6 strong rubber bands
1 wedge-shaped piece of wood or plastic (e.g. a door wedge)
Examples of wedges such as an axe head, chisel, or pizza cutter
An apple or potato
A sharp knife (not serrated)
What to do:
1. Join the two blocks of wood or polystyrene together using three rubber bands at each end.
Invite a student to pick them up and try to pull them apart with their hands. They should find it
difficult.
2. Place the blocks on the table, and tell students you have a machine that will enable them to
separate the blocks with just one hand. Place the thin end of the wedge between the two
blocks.
3. The student should be able to push down with one hand, or just two fingers, and separate
the blocks.
4. Examine the triangular shape of the wedge with the students, noting how it is wide at one end
and thin at the other. Note the similarities with the shape of your other wedge examples. Point
out that students have wedges in their bodies – their front teeth.
5. Trying cutting the apple or carrot with the top, unsharpened side of the knife. Then turn the
knife over and use the wedge-shaped blade, noting the difference in effort required.
Discussion:
Wedges are like two inclined planes put together in a ‘V’ shape. Rather than have the load pulled
up them, they are pushed down into the load. A small effort force downwards is magnified into a
larger sideways force that separates the material.
Cross-curricular Link: Students could research early use of wedges, such as ploughs or tools
such as arrow heads. They could make a model of a machine or tool using authentic materials.
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Activity 1c: The turn of the screw
Teacher notes
Summary:
Part A Students go on a ‘Screws and Bolts’ treasure hunt, describing all the different ways they are
used in the classroom.
Part B Students wind paper inclined planes around pencils to create screws with different threads
and pitches, which they measure.
Part C Students investigate real screws or nuts and bolts (which are perhaps more suitable for
younger students). They may use a screwdriver to drive different screws into some wood, or wind
a nut onto a bolt. Students could use a screwdriver to take apart some old toys or appliances or
watch a car jack being used (an excellent visual demonstration of a long screw).
Aim:
To raise awareness of the use of screws as fasteners in common objects.
To demonstrate that a screw is an inclined plane wrapped around a cylinder.
To explore ‘pitch’ and demonstrate that the longer the inclined plane, the more turns of the screw
are needed to drive it in.
Part A: ‘Screws and Bolts’ treasure hunt
No equipment needed
What to do:
Begin by asking students how they think their chairs and desks are held together, or how the door
is attached to the door frame. Point out where the screws are located. Give them a ten minute
time limit to find and list as many examples of where screws or bolts (which have nuts to hold
things in place) are holding things together in the classroom.
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Part B: Model screws
What you need (per student or pair of students):
3 pencils or pens identical in width
1 pair of scissors
1 copy of the screw template sheet (see p x)
Sticky tape
A screw or nut and bolt set
What to do:
1. Have students examine a screw or bolt. Explain that the curly, spiral part is called the thread,
and that it is wrapped around a central cylinder part. Use a screwdriver to demonstrate how
turning the screw sinks it down into wood. Tell them they will create some model screws.
2. Students shade in the long, sloping side of each triangle on the screw template sheet and cut
the triangles. They tape the shortest side to the pen or pencil and wrap the triangle around to
create a thread pattern.
3. Students draw the different thread patterns, record how many times the thread is wrapped
around the screw and measure the width of the pitch.
The aim is to link the slope of the triangle, the number of turns of the thread and the pitch.
A gentler slope means a longer inclined plane, which means more turns of the thread and a
narrower pitch. This means you need to turn the screw many more times to get it into the wood,
but it should be easier to turn.
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Part C: Bolts, nuts and screws
What you need (per student or pair of students):
2 nut and bolt sets, with a similar diameter, but different pitches
OR
2 screws with a similar diameter, but different pitches
AND
A block of softwood with holes for the screws drilled into it AND
A screwdriver
What to do:
Have students investigate their nuts and bolts or screws.
They could:
• Count the number of turns needed to wind the nut on, or drive the screw into the wood.
They will need to mark the screwdriver or bolt to do this accurately.
• Count the number of turns on their bolt or screw by wrapping a piece of string around from top
to bottom. Unwrapping and measuring the string gives the length of the thread (which
corresponds to the long side of the triangles in Part B activity) – the total distance the screw
must be turned.
• If they have two different screws, they could compare the number of turns and how easy it is to
get the screw into the wood a certain distance.
• (Screws with a narrower pitch require more turns, but it should feel easier to drive them in)
• Look for other differences, such as Phillips head and flat head screws.
Discussion:
The ramp or inclined plane that winds around the screw is called the thread. The vertical distance
between turns of the screw is the pitch. The thread corresponds to the distance through which the
screw is turned. The longer the thread, the smaller the pitch and the greater distance it must be
turned.
A car jack has a long thread that must be turned many times, but the result is that your effort force
is greatly magnified, and the car is lifted (the ‘force-distance trade off’ at work again).
Cross curricular link:
Students could research and build a model of the Archimedes Screw - one of the earliest machines
still in use today.
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Activity 1c: The turn of the screw
Name:
Student worksheet
……………………………………………………….
Aim:
To look for everyday objects that are held together with screws or bolts; to create models of screws
with different thread patterns; to investigate the thread patterns of real bolts or screws.
Part A: ‘Screws and Bolts’ treasure hunt
Screws and bolts are used everywhere to hold things together – you will be
surprised once you start looking.
List all you can find screws and bolts in the classroom. Draw one example.
Part B: Model screws
What you need:
3 pencils or pens identical in width
1 pair of scissors
1 copy of the screw template sheet (page 44)
Sticky tape
A screw or nut and bolt set
What to do:
1. Colour in the longest side of each of triangles A, B and C on the template. Measure this side,
and write it down below.
A: ……………… cm
B: ……………… cm
C: ……………… cm
Which triangle would you say has the ‘steepest’ slope?
………………
Which triangle has the ‘gentlest’ slope?
………………
2. Cut out the triangle, tape the shortest side to a pencil and wrap it around to create a ‘screw’. As
you wrap, count how many times the paper goes around the pencil. Use some tape to stick the end
down.
3. Line up your three pencils in front of you. You should see three different patterns, like the
grooves on a real screw. This pattern is called the thread. Each line on the thread is one turn of
the paper.
Draw the three screws you have made, with the three different thread patterns. Label your screws
A, B and C, after the triangles used to make them.
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4. If your pencil screws were real screws, how many times would you need to turn them to screw
them down into a piece of wood?
(Think about how many times you wrapped the paper around the pencil).
Screw A would need ……………… turns
Screw B would need ……………… turns
Screw C would need ………………turns
5. The distance between two grooves on screw is called the pitch. Measure the pitch for each of
your screws.
A: ……………… cm B: ………………cm
C: ………………cm
Which screw has the widest pitch?
…………….…
Which screw has the narrowest pitch?
…………….…
Can you spot a connection between the length and slope of the triangles, the number of turns of
the thread and/or the size of the pitch?
Write anything you notice here.
Part B: Bolts, nuts and screws
Your teacher will give you two different types of bolts and nuts, or two
different screws. Your task is to investigate them.
You could find out:
• How many times you need to turn the nut to get it all the way from the
bottom all the way up to the head of the bolt. OR
How many turns it would take to get the screw down into the wood.
• How long the thread of the screw or bolt would be if you could ‘unwrap’ it?
• If you have two different screws, which one is easier to screw into wood?
Use this space for drawings or working out.
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Activity 1c: Screw Template Sheet
C
B
Colour the longest side of
each triangle and cut them
out.
Tape the shortest side to a
pencil and wrap it around to
create a screw.
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A
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Activity 2a: Wonderful wheels
Summary:
A simple student activity or teacher demonstration that can be extended into a more detailed
investigation of friction and the factors affecting it.
Aim:
To demonstrate how wheels are used to reduce friction.
What you need:
1 force meter, spring or rubber band
1 roller skate, skateboard, small cart or trolley
What to do:
1. Place the skateboard, roller skate, cart or trolley upside down or on its side on the floor or
bench. Alternatively, if you can remove the wheels, do so.
2. Attach a force meter and measure the amount of force necessary to move it steadily across the
floor or bench. If you are using a spring or rubber band, measure the stretch.
3. Place the skate or cart on its wheels, or reattach the wheels.
4. Measure the force required to move it steadily now.
Discussion:
Friction is a force that acts whenever two surfaces, such as the floor and the skateboard, slide past
each other. Friction always opposes motion and slows things down. Rolling an object instead of
sliding it produces less friction. You may find that it takes more force to start the object moving
than it does to keep it moving at a steady speed – the force meter ‘gives’ a little once it is moving.
This is because the friction force changes – the friction that holds an object in place and stops it
moving is greater than the friction that slows moving objects down.
Extension:
The force of friction can vary, depending on the surfaces involved. Experiment by measuring the
force required to drag an object (such as a shoe) across different surfaces.
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Activity 2b: Wheels and axles at work
Summary:
A two part activity investigating wheel and axle machines. Either part may be done separately.
Part A may be done in conjunction with the ‘Turn of the screw’ Activity 1c. Part B involves close
observation and sketching of devices that contain wheel and axles.
Aim:
To observe how a wheel attached to an axle can reduce the effort required to perform a task. To
identify the wheel and axle parts of various devices.
Part A: Screwdrivers
What you need:
A screw firmly embedded in a block of wood
A screwdriver
String
What to do:
1. Try to remove the screw from the block of wood by using one hand to turn the metal shaft of
the screwdriver, NOT the handle. Can you do it?
2. Now use the screwdriver as it is meant to be used – by turning the handle. Is this easier or
harder than using the shaft?
3. Use the string to measure how far the shaft moves in one full turn of the screwdriver.
4. Now use the string to measure how far the handle moves in one full turn of the screwdriver.
Which moves further – the handle or the shaft?
Handle
Shaft
Part B: Wheels and axles at work
What you need :
A selection of wheel and axle devices, such as: doorknobs, pepper and coffee grinders, taps, wind
up toys, can openers, toy cars.
What to do:
1. Select one or two of the devices with wheels and axles. Examine them closely and draw a
simple diagram.
2. See if you can identify the wheel and the axle. Label them on your diagram. Describe how the
device works (a flowchart may be useful for this). Is the device a force magnifier or a
movement magnifier?
Discussion:
The screwdriver is a wheel and axle machine, with the handle as the wheel and the shaft as the
axle. Screwdrivers, door knobs and taps are force multipliers – turning the wheel with a small force
turns the axle with a larger force. The trade-off, however, is that the wheel must be turned through
a much greater (circular) distance than the axle. Car wheels and fans are movement multipliers –
the wheel or fan blades move further in one turn than the axle does (but turn with less force).
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Activity 3a: The law of the see saw
Teacher demonstration
Summary:
A whole class, teacher led investigation exploring how balance can be achieved with objects
(people) of different masses.
Aim:
To introduce the concept of a lever and its parts – effort, fulcrum, load.
To establish the ‘Law of the see saw’ - the further away the effort from the fulcrum, the easier it is
to lift the load.
What you need:
A playground see saw OR
A plank of wood, 4-5cm thick and wide enough to stand on
A large wooden block, brick or pipe – something to act as a fulcrum
What to do:
1. Pose some questions: How could two people stand on the plank and have it balance with both
ends off the ground? Who would it be easiest to balance with? Have them identify someone
they think they could balance with, and get pairs of volunteers to have a go at balancing. Why
did they choose that person to balance with?
2. Explore what happens when one person moves forwards or backwards along the plank.
3. Now ask: ‘If I got on the plank – could you lift my end up and balance me?’ Discuss where you
should stand, and where a student should stand. Add another student if one is not enough.
Ask ‘what could we do to the plank to make things balance?’ Direct their responses towards
making their side longer.
4. Back inside the classroom, have students draw a diagram of the see saw, with the teacher on
one end being balanced by students on the other end. Introduce the terms ‘fulcrum’, ‘load’ and
‘effort’ and have them label their picture.
Discussion:
The see saw is a type of a machine called a lever. Levers always have three parts: the load (the
thing you are trying to move); the effort (the work you are doing to move the load) and the fulcrum
(the point around which the lever turns, also called the pivot).
A lever is a machine because it is a ‘force magnifier’. This means you can lift a heavy load (like a
teacher) with something lighter (like a student). The longer the lever is on the effort side, the less
effort needed.
Extension:
Construct a mobile using skewers, string and objects of different masses.
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Activity 3b: Lifting the load
Summary:
A simple investigation into how changing the position of the fulcrum affects the amount of effort
required to lift a load. This activity can serve as an introduction to Activity 3c.
Aim:
To physically experience how increasing a lever arm makes lifting a load easier.
What you need (per student):
1 30cm ruler ‘lever’
1 small block or hexagonal pencil as the fulcrum
1 50g mass or equivalent – eg a stack of coins or washers
sticky tape
What to do:
1. Tape the mass to the 30cm end of the ruler. Place the fulcrum 5cm from the other end.
2. Lift the weight by pushing down on the end of the lever. Note how difficult it is.
3. Now move the lever so the fulcrum is under the 10cm mark. Try to lift the weight again. Is it
easier or harder this time?
4. Repeat the process with the fulcrum at the 15cm and 20cm marks. You should notice a marked
difference in the amount of effort required to lift the weight. You should be able to lift it with one
hand or one finger.
Discussion:
Draw four simple diagrams to representing the 20cm, 15cm, 10cm, and 5cm fulcrum positions.
Label them to show when it was hardest to lift the weight and when it was easiest. Describe what
happened as you made your end of the lever longer. Try and summarise your results with a rule.
Why do you think this type of lever is called a ‘force magnifier’?
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Activity 3c: Location, location, location!
Teacher notes
Summary:
Students use different amounts of coins or small masses to balance each other on a ruler. They
measure the distance of the effort and the load from the fulcrum, and look for patterns in their data.
Aim:
To establish the relationship between load, effort and distance. To introduce the concept of
‘mechanical advantage’.
What you need:
6 identical masses, such as washers or 10 cent coins
30cm ruler
1 pen or marker - a hexagonal pencil works well
3 small sticky notes
What to do:
1. Have students construct a lever by taping the pen or pencil to the table and balancing the ruler
on top – the 15cm mark should be on top of the middle of the pencil. This is the fulcrum of the
lever – it is important that this doesn’t shift during the experiment.
2. Have them label the effort (‘E’), load (‘L’) and fulcrum (‘F’) on their ruler using the sticky notes.
3. Students add masses to the load side of the lever at the distances specified in the table on
their worksheet. They then try and balance the load with a certain number of ‘effort’ masses by
placing them at different distances from the fulcrum.
Example: one ‘effort’ mass placed 10cm from the fulcrum will balance two ‘load’ masses 5cm
from the fulcrum.
Note: Students may find they need patience to get the distances ‘just right’ so the lever balances.
Discussion:
The ‘lever principle’ states that ‘the longer the lever arm, the easier it is to lift the load’. The lever
arm is the distance between the effort and the fulcrum. Students should find that to lift a heavier
mass with a lighter one, the lighter one must be placed further away from the fulcrum.
They should also find that the product of the effort and its distance from the fulcrum is equal to the
product of the load and its distance, i.e.
mass (effort) x distance (effort) = mass (load) x distance (load)
Whilst this looks similar to the work equation w = f x d, note that it is not the same, as the ‘f’- refers
to the weight (in newtons) of the load or effort, and the ‘d’ refers to the distance they move up or
down, not the distance from the fulcrum.
‘Mechanical Advantage’(MA) is a number that describes how much a machine ‘magnifies’ force.
It is calculated by dividing the Load (Output Force) by the Effort (Input Force).
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Activity 3c: Location, location, location!
Student worksheet
Aim:
To lift a load with a smaller effort. To find a connection, or relationship between load, effort and the
distance from the fulcrum.
What you need:
6 identical masses, such as washers or 10 cent coins
30cm ruler
1 pen or marker - a hexagonal pencil works well
3 small sticky notes
What to do:
1. Tape the pen or pencil to the table. Balance the ruler on top – the 15cm mark should be on top
of the middle of the pencil. This is the fulcrum of the lever – it is important that this doesn’t shift
during the experiment.
2. Write an ‘L’ on one sticky note and stick to one side of the ruler – this will be the ‘load’ side.
Write an ‘E’ on another sticky note and put it on the ‘effort’ side. Write an ‘F’ on the third sticky
note and stick it on the pencil – this is the ‘fulcrum’.
3. Place one weight or coin 5cm from the fulcrum. Balance it with one weight or coin 5cm away on
the other side.
Now place two coins 5cm from the fulcrum. Can you make it balance with just one coin? Where do
you have place the coin?
Add a third coin to the other two, and balance it with the single coin.
Record your results in the table below. Make sure you measure from the centre of the fulcrum to
the centre of the coin.
Try the other combinations of coins and distances in the table, filling in the distance you need to
make things balance.
Make up one new combination of your own that balances and record it in the table over the page.
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Number of
masses/coins
1
2
3
2
3
3
4
LOAD
Distance from fulcrum (cm)
5
5
5
7
6
4
3
Number of
masses/coins
1
1
1
1
EFFORT
Distance from fulcrum
(cm)
9
2
12
Analysing your Results:
1. Circle the words that make this sentence correct:
‘As I increased the number of masses on the Load side, I had to move the single mass closer
to/away from the fulcrum.’
2. Look closely at the numbers for mass and distance in the ‘load’ side of the table. Now look at the
numbers on the ‘effort’ side of the table. Are these numbers connected in some way? Try and
describe any pattern that you can see in the data.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. You have three masses 2cm from the fulcrum. Where could you put one mass to balance this
Load? ____________________________ Test your prediction. Were you correct? ____________
4. Try and write a rule that links the effort and its distance from the fulcrum with the load and its
distance.
Extra for experts - ‘mechanical advantage’:
The ‘mechanical advantage’ (MA) of a machine describes how much bigger the machine makes
the input force.
We use a simple formula to calculate it:
MA = load ⁄ effort
For example, if we lift 4 coins with only 2 coins on a ruler lever:
MA of 4 ⁄ 2 = 2.
The lever is lifting a load that is two times greater than the effort.
Which arrangement in your results table gives the greatest MA?
Use the formula to calculate it.
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Activity 3d: Lever launch
Summary:
Students construct a simple catapult that is a first class lever. They experiment by changing the
position of the fulcrum and observing the effect on the distance a missile can be launched.
This activity is a good opportunity to develop understanding and skills in the scientific method.
Aim:
To make a simple catapult and experiment to find the best design for hitting the target.
What you need:
2 plastic or paper cups
1 wooden skewer
1 ruler
Blutak
A target (either a small object or an ‘X’ on a
piece of paper)
What you do:
1. Make two holes on opposite sides of each cup, about 1cm from the bottom. Stand the cups
upside down and thread the skewer through them. Put some blutak underneath the ruler at the
20cm mark, and stick the ruler across the skewer so the 0cm end is touching the table.
2. Place your ‘missile’ on the lower end of the ruler and launch it by pushing down on the other
end. Your partner may need to hold the cups in position, or you could tape them to the table.
3. Make the catapult arm longer by sticking the ruler down at the 26cm mark. Launch your
missile again. What difference has a longer arm made?
4. Place your target a ruler length (30cm) away from the base of your catapult.
Your challenge now is to work out how to change your catapult so that your missile lands as close
to the target as possible. You will need to do some tests and make measurements. You will also
need to think about all the things that could affect where the missile lands, and how to keep your
tests ‘fair’. Once you have done your tests, write a report on what you did and what you found out.
Discussion:
Your catapult is a first class lever. The fulcrum is the point where the ruler is stuck to the skewer,
the load is your ‘missile’ and the effort is you pushing down on the other end.
Extension:
Do some research on types of catapults used in ancient and medieval times, such as the
mangonel and trebuchet (sometimes called a trebucket).
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Activity 4a: The power of pulleys
Summary:
This activity investigates the effect of increasing the number of pulleys on the effort required to lift a
load. Cotton reels, wire and dowel make good substitutes if actual pulleys are not available. A
rubber band, spring or force meter can be used to measure force. To investigate the ‘forcedistance trade-off’, measure both the height the load is lifted and the distance through which the
string had to be pulled to lift the load to that height.
Aim:
To demonstrate how one pulley can be used to change the direction of an effort force. To
demonstrate the effect of two or more pulleys on the effort required to lift a load.
What you need:
A force meter (or spring or rubber band)
4 cotton Reels all the same size
A 20cm piece of dowel/bamboo that the
cotton reels can be threaded onto
1m String
coat hanger wire (or wire of a similar
thickness)
Strong sticky tape
A 500g mass or similar ‘load’, such as a cup
full of counters or sand
What to do:
1. Attach the load to be lifted to the force meter.
2. Measure the amount of force needed to lift the load by pulling up on the force meter.
3. Thread a cotton reel onto the dowel. Tape the dowel across the gap between two desks. Hang
the string over the cotton reel, with the weight on one side, and the force meter on the other.
4. Gently pull down on the force meter to lift the weight. Measure and record how much force is
needed.
5. Tape a second dowel in the gap. Untie the load and tie the end of the string to the centre of the
dowel. Create a ‘running pulley’ by threading a short length of wire through a second cotton
reel, then bend the ends of the wire down and attach them to the load. Thread the string under
the running pulley and up over the top of the other, ‘fixed’ pulley. Attach the force meter,
measure and record the force required to lift the weight.
6. Create a four pulley system by adding an extra cotton reel to both the fixed and running
pulleys. Thread the string down and up over each of the pulleys, as shown, and attach the
force meter. Gently pull down to measure the force required now, and record it.
Discussion:
As you increased the number of pulleys, what happened to the force you needed to lift the load?
What happened to the length of string that you had to pull?
Try and explain your observations.
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Activity 4b: Pulley tug of war
Teacher led demonstration
Summary:
A teacher-led demonstration of how a pulley machine magnifies the input force, this activity does
not use any actual pulleys. The sight of one small student pulling together two larger ones usually
gets quite a reaction from the rest of the class.
Aim:
To demonstrate how a pulley system can magnify your input force.
What you need:
2 thick wooden broom handles
A long (several metres) piece of rope
3 students (the visual impact is heightened if one is smaller than the others)
What to do:
1. Ask the two larger students to stand about one metre apart, and each hold a broomstick out
in front of them, parallel to the ground.
2. Stand the smaller student at the end of the broom handles, in between the other two
students. Give them the rope and ask them to use it to pull the other two together. They
may not attach the rope to the other students, or lasso them!
3. After different ideas have been tried, tie one end of the rope around one end of the broom
handle, then loop it around the other handle and back around, four or five times.
4. Have the smaller student pull hand over hand on the end of the rope (it can help if they
stand slightly off to one side), while the other two pull backwards.
5. Increasing the number of loops between the two handles makes it even easier to pull the
two together.
Discussion:
Point out that the tension force applied by pulling on the end of the rope is present in each of the
sections of rope that lie in between the broom handles. For example, if there are six sections of
rope (not counting the one being directly pulled on), and a force of 10 newtons is applied to the
end, the overall effect is that of 60 Newtons pulling the handles together.
Multiple pulley systems can be explained in the same way. The input force is magnified by the
same factor as the number of rope sections between pulleys (except the one being directly pulled
on). Show some pictures of the block and tackle systems used on cranes or sail boat rigging and
draw comparisons to your broom handle set up.
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Activity 5a: Getting into gear
Teacher led demonstration
Summary:
A kinaesthetic activity where students role play two interlocking gears. They experience the
different rates of rotation of a larger and a smaller wheel. This activity can serve as an introduction
to ’Gears in action’ (Activity 5b) or ’Egg-cellent gears’ (Activity 5c).
Aim:
To experience what it is like to be a tooth on a gear wheel.
What you need:
Rope or chalk to mark circles on the ground
What to do:
1. Make a large circle of 15 or 20 students so that each person is facing the back of the person in
front.
2. Students should place their inside hand on the inside shoulder of the person in front. They then
need to extend their outside arms to make the teeth of a gear wheel.
3. Mark the circle on the ground with chalk or the rope. This marks the path the students are to
follow.
4. Repeat these steps to make a small gear wheel with five students. Make sure the students are
facing the correct way and that the two circles are close enough together so that one arm of
one wheel will fit between two arms of the other wheel.
5. Ask the large gear wheel to walk slowly once around their circle. (They will need to take note of
their starting position to make sure they end up there). The ’teeth’ of the gears have to stay
interlocked at all times. This means the smaller gear wheel will have to move as the big gear
wheel moves.
6. Once the big gear has done one rotation, stop and discuss how the smaller gear moved.
7. Try different numbers of teeth on each wheel, for example (16, 4), (10, 5), (10, 10) and so on.
(Keep the big gear number a multiple of the small gear for ease of discussion).
Discussion:
How many times did the small wheel turn when the large
wheel turned once?
What was it like being in either wheel – did you move
differently? How?
In which direction did the wheels turn
(clockwise/anticlockwise)?
How could you use gears to speed up or slow down a
rotation?
(From: Gianello, L. (ed) (1988) Getting into Gear: Gender inclusive teaching strategies in science.
Curriculum Corporation.)
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Activity 5b: Gears in action
Teacher notes
Summary:
Students connect two, then three gears together and explore some basic principles relating to
them, using Student worksheet 1. Student worksheet 2 is an extension sheet that explores gear
ratios in more mathematical detail. Sets of different sized gears can be purchased fairly cheaply
from school suppliers. Alternatively, ‘ridged’ jar lids (such as those on drink bottles or vegemite
jars) with holes punched in the middle work fairly well. The ridges on the lids mimic the gear teeth;
however, some care is needed when turning to make sure they don’t slip.
Aim:
To set up and investigate different gear systems. To observe that the rotation of a gear wheel
depends on it’s size and connections to other gear wheels.
What you need:
3 gears (or lids), two of the same size, and one larger, labelled A, B and C (or painted three
different colours)
1 balsa, foam or polystyrene base
Short nails OR skewers to attach the lids/gears to the base
2 rubber bands
2 different coloured felt-tipped pens
What you do:
1. Students fasten two gears to the base using skewers or nails. (See Picture 1 on Student
Worksheet 1). The gears need to be touching – use the rubber band to keep the contact firm.
Students should mark where the lids are touching – this is the starting position.
Students turn gear A one full turn clockwise, and observe that gear B turns with the same
speed in the opposite direction. They turn A anticlockwise, and note that gear B also
changes direction.
2.Gears A and B are moved back to their starting position and the larger gear C is added so that it
is touching gear B. They secure it with a rubber band and draw another coloured mark where
gears B and C are touching (See Picture 2 on Student Worksheet 1).
Students turn gear A one full turn clockwise and observe the direction and speed of gear C.
The key observation should be that gear C turns in the same direction as gear A, but more
slowly.
3. Students remove gear A and use gear B to turn gear C.
4. Students use gear C to turn gear B.
They should note they must turn gear B several times to get gear C to turn once. Using
gear C to turn gear B results in gear B turning faster than gear C.
Discussion:
When a small gear is used to turn a bigger gear, a bigger force is produced. This is called ‘force
magnification’. An example is riding your bike in low gear – it is easier to pedal, but you have to
turn the pedals more times (this is the ‘force-distance trade off’). When a big gear is used to turn a
small gear, we get ‘movement magnification’ - the smaller gear turns a lot faster than the larger
gear.
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Activity 5b: Gears in action
Student Worksheet 1
A gear is a wheel with little bumps, or ‘teeth’ cut into it. Lots of machines use gears. In this
activity you will investigate how gears turn.
What you need:
3 gears, two of the same size, and one larger
1 base to attach your gears to
short nails OR skewers to attach the gears to the base
2 rubber bands
2 different coloured felt-tipped pens
What you do:
1. Attach your gears to the base just like in Picture 1, below. Stretch the rubber bands over the
skewers to help keep the gears in place. Use a felt-tipped pen to label the gears ‘A’ and ‘B’, and
place a mark on each where they are touching. This is the starting position.
PICTURE 1
Slowly turn gear A one full turn clockwise. Observe closely what happens to gear B.
Does gear B turn in the same direction or the opposite direction to gear A? ……………….....
Does it turn faster, slower, or at the same speed as gear A?
…………………..
What happens to gear B if you turn gear A anticlockwise?
…………………..
Label Picture 1 with arrows to show how gear A and gear B are moving.
2. Move gears A and B back to their starting position. Add gear ‘C’ so that it is touching gear B.
Stretch a rubber band around the skewers holding gear B and gear C and use a different coloured
felt-tipped pen to mark where they are touching.
PICTURE 2
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Turn gear A one full turn clockwise. Watch closely to see how gear B and gear C move.
Does gear B move clockwise or anticlockwise? …………………………………………………...
Does gear C move clockwise or anticlockwise? ……………………………………………………
Has gear C completed one full turn?
.........................................……………………………..
How do you know? ……………………………………………………………………………………….
Is gear C turning faster, slower, or at the same speed at gears A and B?................................
On Picture 2, draw an arrow to show gear A turning clockwise. Now draw arrows to show
how gear B and gear C turn. Next to the arrows, write ‘fast’ or ‘slow’ to show how quickly
they are turning.
Cross out the bold words that are wrong:
‘When gear A and gear B are connected to each other, they turn in the same/opposite direction,
with the same/different speed.’
‘When C is added, C turns in the same/opposite direction to A, at the same/at a different speed.’
3. Remove gear A. Put gear B and gear C back to the starting position, and use gear B to make
gear C do one full turn.
PICTURE 3
How many full turns of gear B do you need to make gear C do one full turn? …………………..
Does gear C turn faster, slower or at the same speed as gear B?
…………………..
4. Return to the starting position. Turn gear C one full turn, and count how many times gear B
turns.
How many times does gear B turn if gear C does one full turn?
…………………..
Does gear B turn faster, slower or at the same speed as gear C?
…………………..
When a small gear is used to turn a larger gear (like gear B turning gear C), a bigger force is
produced on the larger gear. An example of this is riding your bike in low gear – it is easier to
pedal (but you have to turn the pedal more times).
When a big gear is used to turn a small gear (like gear C turning gear B), the smaller gears turns
faster. An example is an egg beater. Using the handle to turn the big gear makes the little gears
spin very fast.
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Activity 5b: Gears in action
Student Worksheet 2
Gear ratios:
Gear ratios are often used by engineers and mechanics to describe gear systems.
The first number in a gear ratio refers to the input gear (sometimes called the ‘driving’ gear).
The second number refers to the output gear (sometimes called the ‘driven’ gear).
The numbers used to calculate the ratio are usually the numbers of teeth (sometimes called ‘cogs’)
on each gear.
Gear Ratio = Number of teeth on input gear : Number of teeth on output gear
Example 1:
The pedals on this bike turn an input gear with 40
teeth. This gear is connected by a chain to the
output gear, which has 10 teeth. This gives a
gear ratio of 40:10 = 4:1. This means that for
every one turn of the input gear (the pedal gear),
the output gear (rear wheel gear) turns four
times.
This ratio can also be written as 4/1.
This gear ratio gives movement magnification - because the smaller output gear turns faster than
the larger input gear. However, the larger the input gear, the harder it is to turn the pedals.
Example 2:
Here, the input gear has 10 teeth and the output
gear has 40 teeth. The gear ratio is 10:40 = 1:4
meaning the rear wheel only makes one quarter
of a turn for every turn of the pedal. This ‘low
gear’ system means that it’s easier to pedal, but
you must pedal more to go the same distance.
This ratio can also be written as ¼, or 0.25.
This arrangement of gears, where the gear ratio is less than 1, does not give movement
magnification. Instead, it gives force magnification – even though the output gear turns ¼ as
fast, it turns with four times the force.
Force magnification and movement magnification have an ‘inverse relationship’ – increasing one
decreases the other. Doubling the speed of the output halves the force with which it turns.
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Summary:
Gears
Ratio
What is magnified?
Example
Big turning small
Greater than 1/1
Movement
Top gear on a bike or car,
eggbeaters
Small turning big
Less than 1/1
Force
Low gear on a bike or car,
winch
Activity 1:
Calculate the gear ratios of the three gear sets below. The gear on the left is the input gear.
(A)
(B)
(C)
Gear speed:
Gear ratios are used to calculate how fast an output gear is turning.
To calculate output gear speed, multiply the gear ratio by the speed of the input gear.
Example 1:
The left gear is the input gear. It is turning clockwise at the rate of 20 revolutions
per minute (rpm)
Output gear speed = gear ratio x Input gear speed
= Number of teeth on input gear x Input gear speed
Number of teeth on output gear
= 8/16 x 20
= 0.5 x 20
= 10 rpm anticlockwise (the output turns at half the speed of the input, in the
opposite direction)
Activity 2:
For each of the gear sets in Activity 1, calculate the output speed if the input gear is turning in a
clockwise direction at the rate of 30 rpm. Then try the three gear arrangements here (HINT: you
will need to consider two gear ratios).
(D)
(E)
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SOLUTIONS:
(A)
(B)
(C)
(D)
(E)
(F)
Input Gear Teeth
16
40
24
Input
Gear
Teeth
40
16
16
Middle
Gear
Teeth
24
8
8
Output
Gear
Teeth
8
24
16
Output Gear Teeth
40
24
24
Gear Ratio
Input/Middle
40/24 (5/3)
16/8 (2/1)
16/8 (2/1)
Middle
Gear
Speed
50
60
60
Gear Ratio
16/40 (2/5)
40/24 (5/3)
24/24 (1/1)
Output Gear Speed
12 rpm
50 rpm
30 rpm
Gear Ratio
Middle/Output
Output Gear
Speed
24/8 (3/1)
8/24 (1/3)
8/16 (1/2)
150 rpm
20 rpm
60 rpm
NOTE:
Although the presence of the middle gear in arrangement (F) does not change the output speed,
gear arrangements like this are common because they enable the input and putput gears to rotate
in the same direction. The middle gear is called the ‘idler’ gear.
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Activity 5c: Egg-cellent gears! Teacher notes
Summary:
Students examine the role of the gears in a manual egg beater. They devise and conduct an ‘eggs periment’ to determine the gear ratio - how times the smaller gears turn for one turn of the larger gear.
Aim:
To describe how gears are used to magnify movement in an eggbeater. To see how the number of
teeth and number of turns are related.
What you need:
Several manual eggbeaters (or hand drills if they can be used safely), enough for groups of 2 or 3
Wool or string
felt-tipped pens
2 eggs and 2 bowls (optional)
What to do:
1. Distribute the eggbeaters between groups of students. Get them to examine them closely. Can
they see any gears? How many? Have them each turn the handle while the others observe
how the parts move. Identify the ‘driving gear’ (input) and the ‘driven gears’ (output). Get them
to describe the sequence of energy transfers involved, from turning the handle to turning the
blades. Do the blades move faster or slower than the handle? How c could we prove this?
2. Discuss how they could conduct an experiment to determine how many times the little gears
turn for one turn of the big gear. Establish that the little gears turn the blades, so counting their
turns is the same. Do not spell out how it is to be done, rather, allow them to attempt different
methods they may come up with. Some students will require more guidance than others to
arrive at a workable method, one of which is:
•
•
•
Mark one tooth at the top of the large gear with a pen.
Tie a piece of wool around one of the blades.
One student uses the handle to turn the big gear around
once, so that it has done one ‘revolution’. Another student
counts how many times the coloured wool makes one loop
around the blade.
3. Have students report on what they found. They could write in the formal style of a scientific
report, or use a series of labelled diagrams or a flow chart to describe the steps they took, what
they observed, and their conclusion.
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Extension:
Have students count the number of teeth on the large and small gears (using a pencil to mark them
off as they go is useful). How many times the number of teeth on the small gear does the large
gear have? How is this related to the number of turns the small gear does for one turn of the big
gear?
You could also have one student use the eggbeater to beat an egg whilst the other uses a manual
technique (such as a fork) and compare the results.
Discussion:
The eggbeater is a machine that magnifies movement - the output gears turn much faster than the
input gears, because of their smaller size. How much faster depends how many more teeth the
input gear has. For example, if an 80-teeth input gear turns 10-teeth output gears, they will turn 8
times for every turn of the input gear.
This ‘large input turning a smaller output’ gear arrangement is the one used for ‘top gear’ in
bicycles. Pedalling is harder, but the rear wheel turns several times for each turn of the pedals.
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Activity 5d: Gears – wheely good fun!
Student Worksheet
Summary:
Students devise a method for measuring how far the bicycle travels for every turn of the pedals
and compare this distance for different combination of gears. They use their skills in mathematics
to calculate gear ratios and the speed of the bicycle in different gears. This activity could form part
of a larger investigation into bike science (optimum tire pressure, braking system, friction,
streamlining).
Aim: To investigate the gears and gear ratios on a student bicycle.
What you need (per group of 3 or 4 students):
A bicycle with gears
Measuring tape/metre ruler
String
1. Look carefully at the gears at the front (near the pedals), and at the back (on the rear tyre) of the
bicycle. The chain can connect any two gears together. How many gear combinations are
possible? Wheel the bicyclee along and change the gears (the device on the back wheel that
does this is called the ‘derailluer’).
Number of front gears: ________ Number of back gears:_________
Number of gear combinations:_________
2. Change the gears so that the smallest front gear is connected to the largest back gear. This is
the lowest gear setting. Using your string, measuring tape or other equipment, devise a way of
measuring how far the rear tire turns when the pedals are turned through one full turn. You
might like to wheel the bicycle along, turn it upside down or have group members hold it up so
the wheels can spin freely (make sure you don’t allow the rear tyre to spin past the point that the
pedals pushed it to.)
3. Repeat your method for the highest gear setting (the biggest front gear turning the smallest back
gear), and for an ‘intermediate’ gear combination.
Describe your method (use a diagram to help), and record your results here. Use the back
of this sheet if you need more space.
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Gear ratios:
The gears on bikes (and also cars) are often described using ‘gear ratios’. A gear ratio is written
as the number of teeth on the input gear (the front, pedal gear on a bike) compared to the number
of teeth on the output gear.
Eg: A 24-tooth front gear on a mountain bike is connected to a 30-tooth back gear.
Gear ratio = 24:30
Simplified Ratio = 4:5
Unit ratio = 0.8 :1 (4/5 :1)
This means that every time the front gear goes through one full turn (one revolution of the
pedals) the larger back gear (and therefore the back wheel) has turned 0.8 of a full turn.
1. Work out the simplified gear ratios for each of the gear combinations you measured in Part A,
using the example above to help you. Record your results in the table below.
Gear
combination
Lowest gear
Front gear
No. of teeth
Back gear
No. of teeth
Ratio
front : back
Unit Ratio
Highest gear
2. Gear ratios can be used to calculate how far the bike travels for each turn of the pedals. You
first need to work out the circumference of the bike wheels – you could measure this directly
and/or use a formula.
Diameter of bike wheel = _____cm
Circumference of bike wheel = _____cm
Use your gear ratios to work out how far the wheels will travel along the ground with one full turn of
the pedals in both low gear and high gear.
To work out the distance travelled along the ground, you will need to use the circumference of the
wheel. One full turn of the back wheel means the distance travelled is equal to the circumference
of the wheel.
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3. Summarise your calculations in the table below. (One row has been completed as an example,
using a wheel circumference of 1.5m and gear ratio of 0.8:1)
Gear ratio
Example
0.8 : 1
No. turns of
the front
gear
1
Low gear
1
High gear
1
No. turns of
the back
gear
0.8
No. turns of
the back
wheel
0.8
Distance
travelled along
the ground
(0.8 x 1.5) = 1.2
1
4. How well do the distances you calculated in the last column of the table match up to the
distances you measured on the bike at the start? Give some specific reasons for any differences.
5. Your speed on a bicycle depends on how fast you are pedalling and what combination of gears
you are using. Pedalling at 60 revolutions per minute (rpm), means you are doing one full turn of
the pedals every second. Use the distances you calculated in the above table to work out the
speed of the bike in metres per second if you are pedalling at: (a) 60rpm, and (b) 120rpm.
(a) In low gear, speed = ……………….m/s
= ……………….km/h
(b) In low gear, speed = ……………….m/s
In high gear, speed =……………….m/s
= ……………….km/h
In high gear, speed =……………….m/s
= ………………. km/h
= ……………….km/h
Discussion:
How well do the distances you calculated using gear ratios match up with the distances you
measured in Part A? Suggest some reasons for any differences.
Which gear combination would be easiest for pedalling up hills in? What is the ‘penalty’ you pay
for easy pedalling? Why does it get harder to pedal as you move up towards top gear? When
would you use top gear? Why do you think bicycles such as mountain bicycles can have 20 gears
or more, while track bicycles have very few?
http://www.exploratorium.edu/cycling/gears1.html has information that can help your understanding
of bicycles and gears.
http://www.powerhousemuseum.com/hsc/bike/history.htm gives a good history of how bicycles
have developed over time.
Extension:
Investigate other aspects of bicycle technology. See how many simple machines, such as levers, you
can identify. You might like to measure the forces involved in braking, or the effects of different tire
pressures.
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Activity 6: Pumping pistons
Teacher notes
Summary:
Students make and investigate a simple pneumatic system using plastic syringes and tubing.
Filling the syringes and tubes with water makes the system hydraulic, with some observable
differences. This activity can be followed up with the construction activities ‘Robotic Arm’ or ‘Design
a Pneumatic Toy’.
Safety warning:
Remind students that the syringes used in this activity are clean and new. If they ever find a
syringe outside, they should never touch it, but find an adult and report it straight away.
Aim: To investigate how fluid pressure is used to lift and move loads.
What you need:
2 x 20mL syringes
1 or 2 syringes of different volumes
Rubber tubing that fits tightly over the syringe nozzles
What to do:
1. Students join the two syringes by sliding a length of plastic tubing over the two nozzles. It is
important that the plunger of one syringe is pushed in and the other is pulled out when they are
joined.
2. Students push down on the piston that is up and observe
closely what happens to the other piston. In the gas system,
there is a slight ‘delay’ between one plunger being pushed
in and the other moving out. They may also notice that the
plunger they pushed in will spring back slightly towards it’s
original position.
3. The air in the syringes and tubing is filled with water by removing one of the pistons and
carefully pouring water in. The system is now hydraulic, as a liquid (water) is being used
instead of gas (air) to transfer force.
4. Students push the pistons in their hydraulic system and observe closely. Two differences they
should see are that the second plunger moves instantly, and it does not ‘spring back’ at all.
Pose some questions and get students to conduct an experiment to investigate them.
For example: What sorts of things can I push, pull or move with my machine?
What happens if I use different size syringes?
Does the length of the tube make any difference?
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Discussion:
Ask students to report on their investigation. Challenge them to explain how the force travels
through the system, or the differences between the pneumatic and hydraulic systems. If they have
some knowledge of particle theory, they may be able to explain that the delay is due to the space
between particles in gas. This space can be made smaller, i.e. the gas is compressed when the
piston is pushed in. In a liquid, the particles are already close together. Liquids cannot be
compressed, so the force is quickly transferred from one particle to the next. If different sized
syringes are used, students should find that it is much easier to push on the smaller piston than the
larger.
Using a small piston to move a larger one is an example of ‘force magnification’. The pressure in
the tubing remains the same, but is applied over a bigger area (the end of the larger piston). This
means an increase in force on the larger piston. The ‘trade-off’ for an increase in the force being
applied is that the larger piston doesn’t move as far as the smaller one. This can be explained in
terms of a set number of molecules, or volume of water. The long thin cylinder of water being
pushed down by the smaller piston becomes a shorter, wider cylinder at the larger piston.
Using a big piston to move a smaller one results in ‘movement magnification’. The smaller piston
moves further than the larger one, but the resultant force is reduced, due to the smaller area of the
end of the small piston.
Able students might like to take some measurements and calculate the volumes of water that are
moving.
Home learning:
Have students collect pictures of machinery, such as diggers, front end loaders and bulldozers.
Identify where these machines use hydraulic systems to move different parts.
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Activity 6: Pumping pistons
Student worksheet
Summary: Make and investigate a simple pneumatic system using plastic syringes and tubing. This
activity can be followed up with the construction activities ‘Robotic arm’ or ‘Design a pneumatic toy’.
Safety warning: The syringes used in this activity are clean and new. If you ever find a syringe
outside, you should never touch it, but find an adult and report it straight away.
Aim: To investigate how fluid pressure is used to lift and move loads.
What you need:
2 x 20mL syringes
Rubber tubing that fits tightly over the syringe nozzles
1 or 2 syringes of different volumes
What to do:
1. Push the plunger of one syringe down and leave the plunger of the other up. The plungers will
act as pistons.
Join the two syringes by sliding a length of plastic tubing over the two nozzles. You now a have
pneumatic system.
2. Push down on the piston that is up and observe closely
what happens to the other piston.
Write down two or three of your observations.
……………………………………………………………………..
……………………………………………………………………..
……………………………………………………………………..
3. Replace the air in your syringes and tubing with water by removing one of the pistons and
carefully pouring water in. Your system is now hydraulic, as you are using liquid (water)
instead of gas (air).
4. Experiment with pushing the pistons and observe closely. Write down any differences you notice.
……………………………………………………………………………………………………………..
……………………………………………………………………………………………………………..
……………………………………………………………………………………………………………..
5. Conduct an experiment to investigate a question, such as:
What sorts of things can I push, pull or move with my machine?
What happens if I use different size syringes?
Does the length of the tube make any difference?
Discussion:
Write a report on your investigation. Use some pictures to help you explain what you found. You
might even use some maths to measure or describe the movement of your pistons.
Home learning:
Collect pictures of machinery, such as diggers, front end loaders and bulldozers. See if you can
identify where these machines use hydraulics to move different parts.
http://museumvictoria.com.au/Scienceworks/Education/
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