RIC-3531 Primary Science - Book D (Digital)

Bridge Building
Structures – Activity 3
Lesson Focus
Outcomes
Natural and Processed
Materials
2.11 Observes and describes
the characteristics of
common materials.
Indicators
• Investigates the role of
compression and tension
in deciding whether
structures stay up or fall
down.
• Investigates and applies
previous knowledge to
build a bridge spanning
an open space.
Skills Focus
• Communicates
• Designs and constructs
• Investigates
Background Information
Materials have certain
properties which make them
useful. The materials used
to build bridges need to be
sturdy (strong) and also rigid
(stiff).
There are many different types
of bridges.
Arch bridges can be made
of rows of bricks, stones
or concrete. They get their
strength from the arch itself.
Suspension bridges are
supported by huge cables that
span across the gap.
Other types include girder,
truss and cantilever.
Before the Lesson
Materials Needed
Plastic drinking straws, dressmaking pins, pictures of bridges, rulers.
Preparation
Prepare drinking straws and pins for each group. Each group will need about 50
straws and 50 pins. Organise the class into small groups. Organise desks or areas
to be used.
The Lesson
Stimulus
Show students pictures of a variety of bridges and discuss any bridges in the local
community. Discuss how a simple bridge such as a log over a stream can work
well, but when the distance to be spanned increases, there is a need for special
forces to be controlled by engineering. It is important that students be provided a
‘free-play’ time to get rid of excess excitement related to the materials. Students
could be asked to make as many different shapes as they can.
What to Do
• Explain the task of constructing a bridge over a 40-cm span.
• In this activity students will be required to apply knowledge from previous lessons.
• As in the first activity, ask the class to agree on a set of rules that each group must
abide by when constructing its bridge; for example, ‘The bridge is allowed to be
fixed to the desk using tape’. These rules will ensure that the students are working
to the same guidelines and will bring a feeling of ‘fairness’ to the activity. Display
the rules on the board. The students discuss the rules as a group at the beginning
of the activity.
• Testing the strength of the bridge needs to be discussed; however, suspending
metal washers or similar objects of the same size and weight beneath the bridge is
one useful method.
• Discuss how the bridges will be tested for strength and agree on a common
method.
• The students build their bridges. Allow sufficient time for experimentation to
occur.
• Test the strength of the bridges as a whole class.
• Students complete the activity sheet, identifying the strengths and weaknesses of
their bridge.
After the Lesson
Answers
Answers will vary.
Additional Activities
• Complete the same activity using twice the number of drinking straws. Does this
double the strength of the bridge? Can it be longer?
• Students choose one type of bridge structure (beam, cantilever, arch or suspension
etc.) and find drawings and information about it. The students can draw diagrams
of their bridge and use books and the Internet to find examples from around the
world.
Display Ideas
• Display pictures, photographs and postcards of different types of bridges.
• Display the students’ bridges in a safe area.
• Students could sketch bridges in the local area for display or look at photographs
and pictures of famous bridges and paint them.
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56 PRIMARY SCIENCE ~ R.I.C. Publications ® ~ www.ricpublications.com.au
ISBN 978-1-925660-54-8