Simple Machines
C
in the
mmunity
Elementary students in the Philippines explore
the simple machines in their daily lives.
By Robert Bryan, Aris Laroder, Deborah Tippins,
Meliza (Melai) Emaz, and Ryan Fox
T
he community can be a powerful context and minilaboratory for cultivating students’ common understandings of science and mathematics. On the island
of Panay in the Philippines, the community was the
starting place for a group of fifth- and sixth-grade students to
explore simple machines in their daily lives. These students live
and attend school in a rural area where the majority of people
earn their livelihood growing rice, mangoes, papaya, and root
crops such as ginger.
Using small digital cameras, which were purchased locally by
the regional science center for less than $10, pairs of students
captured pictures of simple machines being used to make everyday work in their community easier. They also conducted short
interviews with community members who were using simple
machines to farm and recorded their observations in journals.
What students learned in the process became the basis for
developing the set of culturally relevant lessons on simple machines described in this article.
Each of the examples that follow features a simple machine found
in the community, an explanation of how it works, a guiding-inquiry
question, and a follow-up activity designed to foster students’ exploration of this question.
38 Science and Children
How is this simple
machine used in
the community? In
many rural areas,
people walk a kilometer or more to
obtain their water
from a well. The
tuwang tuwangan
(right), in the Kinaray-a dialect, is
a tool used to fetch
wa t e r f r o m t h e
well. It is placed
o ve r a p e r s o n ’s
shoulder and buckets of water are placed on both of its ends. The fulcrum
of the tuwang tuwangan is the person’s shoulder. The
buckets of water are both the load and effort depending
on which needs to be adjusted. As the bucket feels heavy
on one side, the man’s arms adjust the appropriate load
and effort by moving the pole slightly.
How does a lever work? A lever is used to lift heavy
objects or to pull objects apart. Levers pivot on a point
known as the fulcrum. When using a lever, a person
pushes or pulls on part of the lever in order to move,
separate, or lift another object. The push or pull the
person does is sometimes called the effort force. The
force of the object that is going to be moved or lifted is
called the load.
There are three types of levers, and the positions of
the fulcrum, effort force, and load determine the class of
a lever. A first-class lever, which is like a seesaw, has the
fulcrum in the middle of the lever. Pushing down (effort
force) on one end of this lever lifts the object on the other
end (load). A second-class lever is like a wheelbarrow. The
bucket of the wheelbarrow (load) is in the middle of this
lever. The fulcrum is at the wheel and the long handles are
where a person lifts up (effort force). A third-class lever
is like a fishing pole. The person lifts (effort force) in the
middle of this lever. The fish is pulling down (load) at
one end of the pole and the pivot point (fulcrum) is at
the other end of the pole. Third-class levers are different
from other levers because they do not make work easier
(decrease the effort force).
Guiding-Inquiry Question: What happens when the
distance is changed between the fulcrum and the effort force?
Exploration: The Coin Seesaw
Materials: Five coins or washers, 30 cm ruler, pencil
Procedure: Place the coins or washers (load) on top of
the ruler at the 1 cm mark. Place the pencil under the
ruler at the 10 cm mark. Push down on the 30 cm mark
(effort force). Move the pencil to the 15 cm mark and
push down at 30 cm (effort force). Compare your effort
force in steps three and four. Move the pencil to the 20
cm mark and again push down (effort force).
When our students completed this activity, they
recorded the relative resistance (easiest, easy, hard,
hardest) for the various effort arm lengths (the distance
of the downward push from the fulcrum) in a chart and
answered the following questions:
•What class of lever is this? (First)
•Why is this important? (Work is made easier and
the fulcrum is in the middle.)
•Based on your data, which would be easier to push
down; an effort arm of 30 cm or 40 cm? (40 cm)
Simple Machine: Pulley
How is this simple machine
used in the community?
Many people dig deep wells
to ensure a steady supply of
water. A pulley (right) is
used to transfer water from
a deep well easily.
How does a pulley work?
Pulleys change the direction of a pulling force. We
pull downward and the
object on the other end of the pulley moves upward. A
pulley is usually a wheel that has a groove around the
outside edge. The groove is for a rope or belt to move
around the pulley. Work is made easier because pulling
down on the rope is made easier due to gravity.
Guiding-Inquiry Question: What happens when you
increase the number of pulley turns?
Exploration: Lifting Brooms
Materials: Two thick plastic broom handles
(Thick plastic broom handles should be used to
reduce the chance of wooden ones breaking in
half); one 2.5 m long piece of rope
Procedure: In this activity, students investigate the
work done when increasing the number of pulley turns.
Have one student tie the end of the rope onto one of the
broom handles. Have two students stand about 76 cm
apart so that the broom handles are about 1 m apart.
Wrap the rope around the bottom handles twice. Have a
third student pull on the rope as the other two students
try to hold the handles apart. It should be difficult for a
student to pull the two handles together.
March 2008 39
Photographs courtesy of the authors
Simple Machine: Lever
Now, wrap the rope around the handles two more
times and repeat the previous step. Could you pull the
broom handles together if two strong adults were holding the broom handles apart? With each additional wrap,
it will become easier for a student to pull the handles
together. The greater the number of wraps, the greater
the amount of rope that will need to be pulled in order
to bring the broom handles together. The same amount
of work is being done in both trials (the broom handles
are moving the same distance), but it takes less force to
pull them together because the force is being spread out
over a larger distance (more rope is pulled).
When students conducted the activity themselves,
they recorded the number of pulley turns, the distance
the rope was pulled, and the distance the brooms moved
together on a chart and graphed their data.
Simple Machine: Screw
Simple Machine: Wedge
How does a screw work? A screw is an inclined plane
wrapped around a shaft or cylinder. This inclined plane
allows the screw to move itself, an object, or the material around it when rotated. Screws can squeeze objects
together or move objects in other directions.
How is this simple machine used in the community? A tagad (left)
is used by farmers in the
community when planting rice, corn, or beans.
It is made by sharpening
one end of a bamboo
stick to make it pointed.
The tagad creates a hole
by pushing away the soil.
Then you plant seeds in
the hole. The tagad, like a wedge, uses a downward force
to push something (in this case, soil) sideways.
How does a wedge work? A wedge is two inclined planes
joined back to back. Wedges are used to split objects or
pull them apart.
Guiding-Inquiry Question: What happens when the
wedge is pushed between stacks of books?
Exploration: Stacked Books
Materials: Four hardcover books, any wedge-shaped
object, a tabletop
Procedure: Stack all four books on the table vertically. Push
the tip of the wedge between the second and third books.
Through this activity, students learn data doesn’t always
have to have numbers—it can also be illustrations, symbols, and words, too. Our students recorded their observations in a two-sided journal. On one side of the journal the
students recorded data as a picture, illustrating that when
the wedge is pushed downward into the books, the books
are moved outward. On the other side of the journal, students wrote about where they have seen a wedge-shaped
item used in their community, such as an ax or a plow.
40 Science and Children
How is this simple machine used in the community?
A barena (bottom, photo above) is a metal tool used
by carpenters in the community. It has grooves like
a screw and is used to drill holes.
Guiding-Inquiry Question: Which screw is the easiest
to screw into a block of wood?
Exploration: The Wood Screw
Materials: One block of wood; a screwdriver; four
screws of the same length but with different numbers
of grooves
Procedure: Take the screw with the least number of
grooves. Screw it into a block of wood. Take the screw
with the second-least number of grooves and screw
it into the block of wood. Take the screw with the
second-most number of grooves and screw it into the
block of wood. Finally take the screw with the most
grooves and screw it into the block of wood.
Safety glasses should be worn while using tools.
(You may want to pre-drill holes into the boards
to make this easier.)
Students recorded data on a chart—number of grooves
on screw per cm, number of turns until screw is entirely
into the board, and difficulty to turn (easiest, easy, hard,
hardest)—and answered the following questions:
•If you wanted to drive a screw into something very
fast, what kind of screw would you use? (one with
the least number of groves/threads)
•If you wanted to use the least amount of force to drive
a screw, which screw would you use? (one with the
most grooves/threads)
Note: Some students may define “difficulty to turn”
differently. Some may say that because you have to turn
the screw with more threads more times that it is more
difficult to turn than a screw with fewer threads. Others
Simple Machines in the Community
Simple Machine: Wheel and Axle
How is this simple
machine used in
the community? A
galingan (right) is
a small device for
grinding something
such as coffee, corn,
or rice into smaller
granules. It is made
of two cylindrical
objects made of
stone or wood.
How does a wheel and axle work? Wheels and axles
allow us to turn things easier. A wheel and axle has a
larger wheel (or wheels) connected to a smaller cylinder (axle) so that they turn together. When the wheel
is turned, it moves a greater distance from the axle, so
less force is needed to move it.
Guiding-Inquiry Question: How does the simple machine called the “wheel and axle” make work easier?
Exploration: Spooling Cups
Materials: Two empty spools of thread, string, two
paper cups, 20 coins, two pencils, tape, meterstick
Procedure: This activity has two different setups (see
Figure 1). For Setup A, push the pointed end of the
pencils into each end of a spool (make sure they are
secure). Then punch holes at the top of a paper cup and
attach a string to make a bucket. Tape the other end of
the string to the middle of the spool. Add 20 coins (or
other weights) to the cup, and have the students hold
Figure 1.
Setups for wheel and axle activity.
Setup A
Setup B
both pencils and begin to wind up the bucket by turning
the pencils. For Setup B, insert the pencil between two
spools and tape the bucket to the center of the pencil. To
raise the bucket, turn the ends of the spools. Students
should measure the movement of the cups for both
setups. Which bucket required less force to lift up?
Setup B requires less force to do the same amount
of work (lifting the coins the same height) because the
force needed to lift the cup is spread out over a longer
distance. The circumference of the spools is much
larger than the circumference of the pencil. One rotation of the spool is a larger distance than one rotation of
the pencil. Work, scientifically speaking, is the product
of a force moving an object over some distance (Work
= force × distance). If the same amount of work is being
done by both Setup A and Setup B, and because you
rotate Setup B a greater distance than Setup A, then
the force needed to rotate B must be less than the force
needed to rotate A. While Setup A will require more
force than Setup B, Setup A can lift the cup up faster
than Setup B. This increase in lifting speed of Setup A
may be seen as an easier method to lift the cup by some
students. Because of the quicker lifting, some students
may incorrectly claim that Setup A used less force.
Simple Machine: Inclined Plane
How is this simple
machine used in the
community? A hagdan (right) is a ladder. It can be made
out of bamboo,
wood, or cement. It
is used in Filipino
homes when the
h ou se i s e l e v a t e d
from the ground.
The Filipino homes
are raised as protection from floods or
to provide room for
raising pigs.
Photographs courtesy of the authors
may use the amount of force (how hard they had to turn
the screwdriver) as what they used to determine “difficulty to turn.” It is okay to allow this difference to occur;
use it as a teachable moment to explain how important
it is for us to operationally define terms before we use
them. For this activity, it is best to define “difficulty to
turn” in terms of force needed to turn, not time it took
or number of turns.
How does the inclined plane work? Any sloping surface
can be considered an inclined plane. An inclined plane
can be used to decrease the effort force used in doing
work. Instead of lifting an object straight up with a lot
of force, you can gradually lift the object up by going up
an inclined plane. The tradeoff is that the load must be
moved a longer distance than if it is lifted straight up.
The steeper the inclined plane, the more difficult the
work, but the shorter distance the load must be carried.
The lower the angle of the inclined plane, the easier the
work, but the longer the inclined plane must be.
March 2008 41
Simple Machines in the Community
Figure 2.
Rubric used to access students’ simple machine understandings.
Criteria
Points
Did I draw two pictures of each type of simple machine?
Did I predict the simple machine that would be easier to use?
My prediction was based on what I had researched or observed before.
Did I explain why I chose each simple machine in three or more sentences?
My explanations are clear and correct.
Teacher comments:
Guiding-Inquiry Question: What happens to the
amount of effort needed to move a resistance when the
distance of the inclined plane increases?
Exploration: Transferring Load
Materials: Spring scale; weight (such as a rock); ruler
(30 cm); shoebox; meterstick; flat tabletop
Procedure: Place the shoebox on a tabletop. Place
one end of the ruler on top of the shoebox and the
other end of the ruler on the tabletop. Put the weight
on the lower end of the ruler. Attach the spring scale
to the weight. Slowly move the weight up the inclined plane to rest on the top of the shoebox. Read
the spring scale as you are slowly moving the weight
and record the reading. Next, replace the ruler with
a meterstick (100 cm) and repeat the process described above. Which incline plane required the least
amount of force to slide the weight up to the shoebox?
(The meterstick required less force than the ruler
to complete the work because the weight moved a
longer distance.) Simple machines, like the inclined
plane, do not do the work for you. They just allow you
to use less force spread out over a longer distance.
Scientifically speaking, the same amount of work is
done with both the ruler and meterstick.
Assessment
After completing the explorations on the simple
machines, students were asked to draw pictures of
two different inclined planes, pulley systems, wheels
and axles, and levers that were being used to do some
work. Students were then asked to select (by circling)
the lever, pulley, wheel and axle, and inclined plane
that would be easier to use (use less force). They were
then asked to write three or more sentences explaining why that simple machine would be easier to use
than the other simple machine. A rubric (Figure 2)
was used to assess learning.
42 Science and Children
Self
Teacher
Final Reflections
Our experience using simple machines in the community as the centerpiece of the curriculum reinforced our
belief that science can powerfully engage students when
it is connected to other disciplines and contexts outside
the four walls of the classroom. No matter your setting,
we think you’ll find this an engaging way to explore
simple machines in your classroom, too.
Robert Bryan ([email protected]) is a science teacher
at East Jackson Comprehensive School in Commerce,
Georgia. Aris Laroder is a seventh-grade physical
science teacher at Philippine Science High School in
Iloilo, Philippines. Deborah Tippins is a professor in
the Department of Mathematics and Science Education
at the University of Georgia in Athens, Georgia. Meliza
(Melai) Emaz is a fifth- and sixth-grade science teacher in
the town of Santa Barbara, Iloilo, Philippines. Ryan Fox
is a graduate student in the Department of Mathematics
and Science Education at the University of Georgia.
Reference
National Research Council (NRC). 1996. National science education standards. Washington DC: National Academy Press.
Connecting to the Standards
This article relates to the following National Science
Education Standards (NRC 1996).
Content Standards
Grades K–4
Standard A: Science as Inquiry
• Abilities necessary to do scientific inquiry
• Understandings about scientific inquiry
Standard B: Physical Science
• Properties of objects and materials
• Position and motion of objects