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TECHNOLOGY TERM 2 WORKSHEET: STRUCTURES GRADE 7

They protect, enclose or contain something

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Name…………………………………….. Grade 7…………………… Date……………………………….

STRUCTURES. DEFINITION OF STRUCTURES

A structure is something that consists of many parts held together in a specific way. We see and use many different types of structures every day, each with its own function. Structures give us shelter, spans gap and supports loads. Structures include things like bridges, electricity towers, traditional huts and high-rise buildings. Some structures are old and famous like Zimbabwean ruins and Egyptian pyramids. Others are new like Nelson Mandela Bridge in Johannesburg and the Cape Town Stadium in Green Point. Classification of Structures: There are two different types of structures: natural structures and man-made structures. Structures that have been constructed by human beings are also known as man-made structures. Structures that occur naturally with no human are known as natural structures.

PURPOSE OF STRUCTURES

Structures are made or constructed for different reasons. Most structures have several functions,

which include:

• To contain things or objects

• To protect and shelter object

• To carry things

• To support loads

• To span a distance

In order to resist force and to avoid structural failure all structures must be:

• strong (unable to break or collapse)

• rigid (unable to bend or change shapes)

• stable (unable to fall over)

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TYPES OF STRUCTURES

There are three different types of structures: Frame, shell and solid structures.

Frame Structures

Frame structures are made from beams connected to each other to support a load. The connected

beams are known as the skeleton. A birdcage is an example of a man- made frame structure.

Shell structure

Shell structures have a solid outer surface, like skin covering your body. They are usually hollow

objects that enclose and protect as part of their function. They can completely or partially enclose

something. The shell of a snail is a good example of a natural shell structure.

Solid Structure

Solid structures are rigid and heavy. They are not hollow like shell structures, instead they are the

same in and out. Solid structures do not take the shape of a container and are not compressible.

Mountains, bricks and stones are examples of solid structures.

.

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ACTIVITY 1.1 Identify structures

Classify the following structures. Write the answers in your books. Natural or man-made. a) Trees Natural f) Skeletons Natural b) Clay pots Man-made g) Caves Natural c) Burglar bars Man-made h) Egg shells Natural d) Plants Natural i) Bridges Man-Made e) Bottles Man-made j) a Truck and trailer Man-Made (10)

Identify types of structures

Copy the table below and classify the following structures as shell, frame or solid structures:

a house; electricity pylon; tortoise shell; cell phone tower; human skull; brick; garden chair; spiderweb; dog

kennel; chicken eggs and rocks.

Shell structure Frame structure Solid structure

human skull garden chair brick

tortoise shell spiderweb rocks

dog kennel electricity pylon

chicken eggs cell phone tower

a house

(10)

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IDENTIFY TYPES OF STRUCTURES

1. Study the structures on the table below and tick to say whether they are natural or man-made frame

or shell as well as their functions.

STRUCUTURE

Natu

ral

Man

-

mad

e

fram

e

shel

l

soli

d

S

up

port

i

ng a

load

S

pan

nin

g a

gap

pro

tect

s

x x

x

x x x

x x x

x x x

x x x

x x x

[15]

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Cellphone Towers

Cellphone phone towers are found everywhere. The construction of towers has to meet many conditions. The popularity of the cellular telephone has made building towers a profitable business. In some countries, private citizens can build cellphone towers and

rent them out to service providers like Vodacom, MTN, Cell C. Cellphone towers are frame structures. Designers and engineers use triangulation to stiffen and support frames. Triangulation What is triangulation? The design and strength of a tower need to fit the purpose therefore mining head mine gear will be different from a cellphone tower. It is easy for rectangular structures to bend under load. All frame structures are designed to resist forces acting on them. Adding an extra member to form two triangles in the structure makes it stronger. This is called Triangulation. Many common structures use triangulation to give them strength including bicycle frames, roofing, trusses and powerline towers. They consist of different beams and struts that withstand tension and compression forces. Beams that make up the structure will support pilling and pushing forces. Beams that resist compression (pushing forces) are called struts. Beams that support forces are called ties. A strong and stable structure can support a load.

ACTIVITY 2: Investigating Cellphone Towers

Look at the pictures of frame structures and complete the questions that follow.

1. Look at the above structures and tell if they are frame or a solid structure? Justify your answer (2)

2. List three materials that you think are needed to buid a cellphone tower. (3)

3. The material on the above two towers is arranged to forms a series of triangles. What do we call this

method of arranging the material? (1)

4. Suggest reasons for the patterns on above the towers. (1)

5. Ropes are used to anchor the first tower on the ground and the second tower is standing on its own.

Can u explain the reason for this difference?. ( 2)

6. Explain what the following structural members are:

a. guys- (1)

b. Ties- (1)

c. Struts (1)

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Activity 3: examine structural elements and design techniques.

Study the four structures below. Pay attention to the following:

• The use of triangulation

• The size of the base

• Appearance

• Suitability for purpose

7. Complete the table below. Rate each structure (1=poor performance and 4 excellent performance) in

each of the categories listed in the first column.

8. Comment on the last column to justify your choice based on your ratings.

.

Triangulation

A

B

C

D

Comment

Suitability for

purpose

Stability

Appearance

(15)

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Stiffen materials and structures The stability of a structure is its ability to maintain and regain its stable position after forces act on it. Strucutures are designed to be strong enough to support the loads they carry. Strucutures also need to be stable so that they do not collapse under the load. We stiffen the marerial to make them stronger and harder.stiffening is the process of adding strength and form to sheet materials or skins.Triangulatin, Tubing, and corrugation or folding are the methods used to stiffen materials

ACTIVITY 4

(Practical) Stiffen a frame structure by triangulation.

Some materials are not suitable as building materials, but their

properties can be changed and improved to make them suitable. You

will now stiffen a flat sheet of paper to make it suitable as building

material for models.

MATERIAL: plastic straws, paper clips, pins or prestik

Method:

1. Use four straws to make a rectangular strucuture.push the square from diagonal corners and observe.

(diagonal corners are opposite and are not next to each other)

Observations…………………………………………………………………………………………… (2)

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2. Use one extra straw as a diagonal member. Push the square from the diagonal corners and record

your observation.

O

Observations……………………………………………………………………………………… (2) 3.Write a few sentences explainning your observations about this strenghthening technique. (3) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ………………………………………………………………………………………………………….

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Activity 5:

Action research: Stiffen paper by tubing

TUBING Papers are strengthened by shaping the into a tube (tubing). Tubing is often used to make frames and for supporting weight. The tube can be the number of shapes; circular, square triangular or eve U-shape.

Individual work.

Material:

• two sheets of A4 paper (preferably wastepaper intended for recycling),

masking tape or sellotape,

• Glue and

• A pair of scissors

Look at the pictures below before you start.

1. Roll a sheet of paper to form a tube with a centre hole that is not bigger than the centre hole of a toilet paper roll. Fasten the tube with tape to keep its shape.

2. Roll a second sheet of paper into a tight tube with a centre hole, so that a pencil can almost not fit in.

3.Fasten the tube with tape to keep its shape.

4.Hold the tubes at their ends. Try to bend each one. Which one bends more easily?

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Folding/ corrugation Corrugation refers to shaping a flat thin sheet into folds. The folding is such that it results in parallel and alternating ridges and grooves. Grooves are furrows. Ridges are elevations. Folding is another way of making material stronger. Corrugated iron and corrugated cardboard are the examples of strengthened folded materials

Activity 6.

Materials: cardboard, sticky tape, a pair of scissors

Also need two books.

Method

1.cut two strips of cardboard each about 30cm long and 8cm wide

2.fold one strip along its length, in the middle so it looks like this

3.which of the two pieces will bend easier? Investigate your answer

4.stick a strip of cardboard on two books at the edged with a sticky tape.

5. press down in the middle of the sheet and observe the results.

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6. Do the same with the folded strip.

7. which strip is the easiest to bend? The flat strip or the folded strip? (1)

8. Explain the above results…………………………………………………. (2)

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Activity 7 (Class discussion)

The impact of Technology

The impact of technology refers to the effects that a technology has on people and the environment. Compare a cell phone (mobile) to a landline phone. First, write a rough copy of the differences in your books. When you write the differences, think of the following: the purpose, safety, cost and the impact on the environment and society. Copy and complete the table below to show the advantages of landline and cellular telephone systems.

Telephones advantages disadvantages

1.Landline telephone

2.Cellular telephone

(4)

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Activity 8 (class discussion)

find relevant case studies from the textbooks, newspapers etc. Read the case study below and then respond to the questions on the following page on your own.

Remember, working alone gives you time to come up with your original ideas. Also remember! there is no

right or wrong answer. Do not get stuck on a part you do not understand.

Case study

Covid 19 is a virus causing thousands of deaths around the world. COVID-19 is mainly transmitted through

droplets generated when an infected person coughs, sneezes, or exhales. These droplets are too heavy to hang

in the air, and quickly fall on floors or surfaces. You can be infected by breathing in the virus if you are within

proximity of someone who has COVID-19, or by touching a contaminated surface and then your eyes, nose or

mouth. South Africa is one of the countries that is badly hit by covid 19 where corona virus is killing large numbers

of people daily. Although the government and is trying hard to save people from losing their lives and flatten the

curve of the virus. At the moment prevention measures are done through the use of sanitisers and facemasks,

however the number of people killed by covid19 is continuously increasing. An assistant professor of mechanical

engineering whose background is in development of novel biosensors and gene editing technology suggested

a use of a device such as cell phone attachment that will act as a microscope and detect germs such as

corona virus "It is urgent for us to better detect, understand, and treat the diseases.

The device should be much faster at collecting the information from an infected person the sooner the better. South Africa government has call upon engineers and scientists to design and make a cellphone with a detector device to minimize the spread of virus, the sooner the better.

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Activity 9

Design Process skills.

1. What is the problem to be solved? (2)

Answer……………………………………………………………………………………………………

2. What is needed to solve this problem? (2) Answer ………………………………………………………………………………………………(1) …………………………………………………………………………………………………………(1)

3. On your own, write a design brief for your proposed cellphone device. (This is a clear and short statement that explains exactly what needs to be done).

Answer…………………………………………………………………………… (2)

4.Write down specifications of your device (specifications must include this):

Size………………………………………………………………………………

Shape……………………………………………………………………………..

Tools ……………………………………………………………………………….

Measurements…………………………………………………………………….

Colour-………………………………………………………………………………

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5.Write down the details of constraints of your design.

(constraints are a list of things that will make it difficult for you to design your proposed tower) such as scarcity of material, time challenges, working alone etc.

Constraints

1.……………………………………………………….. …………………… (2)

2……………………………………………………………………………….. (2)

Activity 10

Make a cellphone with a virus detector

1.List the resources you will need to complete your project.

1…………………………2……………………………3…………………4………………5…………………..

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2.Draw a rough sketch for working for your design showing one face 2D. 2)

2. Draw a working diagram for your design 5

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3. List things you will follow on your planning towards building your device.

Step 1…………………………………………………………………… 1)

Step 2…………………………………………………………………….1)

Step3……………………………………………………………………….1)

Step4………………………………………………………………………….1)

Step 5……………………………………………………………………..1)