1. Types of Structures
Have you ever made a sand castle or an ice sculpture? What about
building an igloo or assembling a tent? Have you peered through a
telescope at another planet, or examined a snowflake under a micro-
scope? All these objects are examples of structures: things with a
definite size and shape, which serve a definite purpose or function.
To perform its function, every part of the structure must resist forces
(stresses such as pushes or pulls) that could'change its shape or size.
For example, a brick wall must be able to stand up to the force of the
wind. The bricks at the bottom must support the weight of the bricks
above. If a person climbs on top of the wall, the bricks must support
that load (the weight carried or supported by a structure) as well.
Many different structures are pictured on these two pages. Look
around your classroom for a moment. Pick out other things you think
could be called structures. In what ways are they similar to each other?
What can you think of that should not be called a structure? Why not?
Write answers to these questions before reading further.
You will learn a lot about
functions, forces, and There are so many different structures that it is difficult to form a
loads in this unit. What definition that fits them all. Instead, we will concentrate on describing
do these words mean to a structure's origin, its function, its form, its design, the materials and
you now? In your parts it is made of, and the ways it is held together. Before reading
Science Log, write a brief further, get together with a partner to develop your own classification
definition of each word,
system for the structures pictured on pages 270-271.
using your own words.
Then write a sentence
.that uses each word Classifying Structures
correctly. It would be inefficient to learn about structures by studying them one,
at a time. There are far too many! It is much more efficient to group,
or classify, structures by picking out those that share common features.
One common classification divides structures into groups according
to their origin. In this system, structures are divided into natural and
manufactured objects.
Natural Structures
Natural stru ctures are not made by people. Examine the photo of a
bird's feather, for example. It has a definite shape, and it is made of
many parts held together in a complex pattern. Feathers serve many
purposes: they insulate birds in cold weather, protect them from rain,
and allow them to fly. Feathers, like many familiar things in the natura
world, are structures.
Non-living parts of the natural world may also have some structural
characteristics. Think of sand dunes, for example. They have a charac-
teristic shape and are made of many parts (sand grains) arranged in a
270 MHR ° Structures and Forces

2. particular pattern. They provide a home for small animals and insects
and play a role in a desert ecosystem. What other natural, non-living
structures can you think of?
Manufactured Structures
Many things built by people are manufactured structures. The largest
buildings, the tiniest beads, a complicated jigsaw puzzle, and a simple
spoon are all manufactured structures. Many manufactured structures
are modelled after natural structures. A fishing net, for example, has a
Figure 4 .1 Canadian
design similar to that of a spider web. Suggest natural structures that wheelchair athlete Stacy
resemble a parachute, an umbrella, and a VelcroTM fastener. Kohut competes in
mountain bike competitions
with his four-wheel bike.
Figure 4 .2 Kayhan Nadji,
the designer of this tipi
house in Yellowknife,
combined elements of the
traditional Inuit Igloo and
Dene tipi with modern
technology such as central
heating and electric lights.
Types of Structures ® MHR 271

3. DATE: NAME: CLASS:
MMa
REINFORCEMENT 1 Classify i ng Structures
Goal ® Develop ways to classify natural and manufactured structures.
What to Do
Complete the table below for the structures on pages 270 and 271 of your textbook. Determine
whether each structure in the left-hand column is natural or manufactured. In the right-hand
column, identify at least one other way to classify each structure. (Hint: How have structures
been described in your classes?) Be prepared to defend your choices. Give the table a title.
Tide:
Structure Natural or manufactured Can also he classified by
sand castle
igloo
planet
snowflake
brick wall
mushroom
bird's feather
comet
sand dune
cactus
wheelchair
the Sphinx
the Eiffel Tower
clay pot
metal pipe
telephone
house/building
jigsaw puzzle
fishing net
spider's web
parachute
umbrella
VelcroTM fastener
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