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Week 26 - Safe Structures, Strengthening Materials and Evaluating Designs

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Course: Science 7 LearnNet
Book: Week 26 - Safe Structures, Strengthening Materials and Evaluating Designs
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Date: Thursday, 18 September 2025, 3:24 PM

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Week 26 - Safe Structures, Strengthening Materials and Evaluating Designs

Table of contents

Exercise 4.1


Lesson 4.1: Building Safe Structures in All Environments


ACTIVITY A: Margins of Safety



Required Readings

Science in Action 7
pages 324 to 328
or
Science Focus 7
pages none


Technology uses scientific knowledge and principles to build practical products. As scientific enquiry uncovers new information about material construction, technologists incorporate that knowledge into new designs and new materials. Above all, the structures that are built must be safe to use. In this lesson we will examine how safety margins are built into the structures we use.

Now that you have read the assignment in the text, define the term 'Margin of Safety' and give and example of how the term is used in the exercise below.

The safety margin for sports equipment is set very high as well. Bicycle helmets must be able to protect the rider's head even when the bike is operated a fairly high speeds. Some old time riders don't feel there is a need for a helmet when riding a bike. But if I asked you to run headlong into a brick wall at your fastest running speed you would think I was crazy! But you and I often travel faster than we can run on our bikes. Do you wear a helmet?

Helmets are an important piece of safety equipment that protects your head if you fall off your bike or are involved in an accident. Helmets must adhere to strict standards and be certified by a national council. To be certified, each helmet design must be thoroughly tested to ensure it stands up to various types of impact. If the helmet fails a certain type of test, it will not be certified and available for purchase. Consumers trust that they are buying a piece of safety equipment that will protect them, so this certification process could be a matter of life and death! This video demonstrates how motorcycle helmets are tested.

In order to build in safety margins you must know the environment it will be operating in. Should the safety margins be the same for race cars and your family car? If they were your family car would be fairly bare and uncomfortable, because you would have to wear a special seat belt, helmet. Your car wouldn't go very far either as the gas tanks in race cars are very small. How about building standards for homes built in Florida and Edmonton? This next section will examine some structural differences in homes from these two environmentally different areas.


ACTIVITY B: Varying Environmental Conditions Determine Structural Safety Standards

Roofs in Alberta's Rocky Mountains need to be designed to carry heavy snow loads.

In Florida, each year hurricane winds destroy many homes and businesses. Usually, the roof is torn off the house first.



The environmental factors that determine the safety standards for homes are quite different when we compare the state of Florida and the province of Alberta. Hurricanes that can rip the roofs off homes are not uncommon in Florida but never happen in Alberta. Heavy snow loads can build up on and crush roofs of Alberta homes, but is not likely to happen in Florida.

How do you think the design of the roof structure might be different in an Alberta home when compared to one found in Florida? Roofs of Alberta homes have strong supporting materials while the roofs of Florida homes are tied to the house by metal fasteners to keep the wind from blowing the roof off.

Each state and province has building codes so that buildings are built with margins of safety for the climatic conditions that are found there.

EARTHQUAKES

During earthquakes some building remain standing while others fall. Why?



The west coast of North America has very active geological activity. Earthquakes are quite common. The building codes for British Columbia and all the western states must account for earthquakes so that an adequate margin of safety is maintained. But how big of an earthquake should they with stand. What about freeway overpasses or bridges?

This overpass collapsed because the pillars were not designed to be earthquake proof.
Exercise 4.1: Disaster Proof Housing


Exercise 4.2


Lesson 4.2: Strengthening Materials to Improve Function and Safety


ACTIVITY A: Make It Better


Required Readings

Science in Action 7
pages 329 to 332
or
Science Focus 7
pages 321 to 329


Have you ever bought something and then found that it wasn't built that well or was unsafe for one reason of another? In this lesson you will find something around the house you aren't entirely satisfied with, and then design a plan to make it better.
Exercise 4.2: Make It Better

Exercise 4.3


Lesson 4.3: Evaluating Designs from an Overall Perspective

ACTIVITY A: The Right Bike for the Right Job for the Right Price


Required Readings

Science in Action 7
pages 334 to 337
or
Science Focus 7
pages none
In this lesson, you will evaluate various bicycles that are on the market. But how do you go about evaluating something? First you have to set up what are called criteria. The dictionary defines the term 'criteria' as a standard of judgment - an established rule or principle for testing anything. In this case, our criteria will be: the use, the cost, the benefits, safety, and the potential impact on the environment.

Consider the following four bikes as to how well they would work in different situations.

BMX bikes are used in many types of competitions like hill racing or stunting. There is a wide range of qualities and prices.



Mountain bikes have many low gears for steep climbing. Many mountain bikes have a full suspension system but can cost thousands of dollars.


Bicycle transport is common in third world countries. These one-speed bikes cost about one month's pay.


Touring bikes are designed for long distance travel over good roads. They can be equipped with saddlebags to carry all your clothes and camping gear. Good bikes can cost thousands of dollars. They are geared to go fast and climb hills. Some have 20 or more gears.

 But bikes aren't the only thing that we evaluate. We make choice everyday on products that we buy, drive, eat, use, and wear. Just walking into a shopping mall sets in motion a whole range of questions in our minds. We have to consider:

  • Does this product meet my needs?
  • Will the product last?
  • Is it aesthetically pleasing?
  • Is it worth the money?

Evaluating products and making thoughtful choices helps us make good choices as consumers. Who wants to spend money on a product, only to realize later that it doesn't meet your needs? No one wants that! If you have considered all the factors before you walk into a store, you will be more likely to purchase something that meets your needs now and in the future.
Exercise 4.3: Evaluating Products

 

Section 4 Notes

You have two options for your Section 4 Quiz - a multiple choice quiz or a written response quiz. You may choose to write the multiple choice or the written response. You only need to write one of them, so the choice is up to you! You are allowed to try both quizzes if you want, but it is not required.

The quiz attempt with the highest grade will be the one that is recorded on your report card.

The multiple choice quiz has 10 multiple choice, matching, and true/false questions. You have 15 minutes to complete it. As soon as the quiz submitted it will be auto-graded and you will receive a grade immediately.

Click the image above to start your quiz

The written response quiz has 5 short answer questions. Your responses must give a complete and detailed answer to the question. You have 20 minutes to complete the quiz. This quiz needs to be manually marked by your teacher, so you may have to wait a few days to get feedback and a grade.

Click the image above to start your quiz