Activity 4: Design and realisation process
Learning objectives
In this learning activity, students are expected to:
 Realise technology as a planned and organised process using resources and
knowledge to achieve human purposes.
 Understand the meaning of design and realisation process.
 Be aware of the limitations of science and technology.
Work allocation
Students will work together in groups of 5 to 6 to perform a design and realisation
activity. Students will apply a scientific theory to solve a technological problem, e.g.,
how to make use of technology to produce a utility for human use. They are requested
to design and perform a realisation process to produce a spring balance for weighing
purpose. Based on the products they have made, students will evaluate the usage of
products and limitations in technology. Students will learn to work collaboratively and
the teacher stimulates students to think and solve scientific and technological
problems.
Activities
Stimulating Recall of Prior Knowledge
State the relationship between the applied force and the extension of a spring or an
elastic material (i.e. Hooke’s Law).
Identification of Need – Application of Scientific Theory
Suggest some applications of the extension of elastic materials (e.g. spring, rubber
band, etc.) in our daily life.
Design Brief and Specification
Design a tool (or a balance) that you may apply the extension of a spring to weigh an
object accurately and state its specification. You may sketch the design in the space
provided. Your specification should:
 Describe what the product has to do.
 State any other requirements that need to be met – how the product should work,
manufacturing methods, materials, ergonomic requirements, etc.
Consideration of Design Factors
Based on your design brief and specification, suggest possible alternatives of their
designs and consider the factors/attributes that may lead to a decision on your final
design.
Realisation – Making Spring Balance
Suggest a brief procedure for making a spring balance with the following materials
provided.
 Spiral spring with pointer
 Stand with an adjustable mirrored scale (15 cm) (Hooke’s Law apparatus)
 Slotted weights
 White label
Product Evaluation
Weigh an object (you may choose any object as you like) with your spring balance
and then with an electronic balance.
Weight of the object recorded by your spring balance:
_________________________
Weight of the object recorded by the electronic balance:
_________________________
Comment on any difference between the above two weighing results.
Limitations of Technology
Suggest some limitations of using your spring balance.
Further Development of Balances
Balance type
Maximum weighing capacity
Accuracy
250 g
0.1 mg
6100 g
0.1 g
50 g
0.1 g
300 lbs
0.2 lb
Baby scale balance
130 lbs (65 kg)
1 oz (20 g)
Bench scale balance
66 lbs
0.05 lb
Analytical balance
Precision
top-loading balance
Pocket scale balance
Body-fat scale
balance
Further Discussion
1. Given the interior construction of a top-loading kitchen balance as shown in the
diagrams below, discuss how the scientific theory of spring extension can be applied
to explain the operation of this top-loading balance.
2. You are requested to build towers with materials such as blocks, Legos, paper cups,
newspapers, straws, etc., to reach specified heights, and with various bases.
Discuss how to build taller towers by alternating the structures (e.g. rolled
newspapers and tape, twisting different materials together, etc.) to find out the best
solution according to the following aspects:
 Designing and creating effective structures for specific objectives.
 Making and testing a product according to functional, aesthetic, and ergonomic
standards.
 Applying different processes for forming, assembling, and testing of materials.
 Making use of recycled materials as resources.
Suggested Procedure for Making Spring Balance
1. Stick a white label on the mirrored scale of the Hooke’s apparatus.
2. When nothing is hung on the spring, label the position of the spring as 0.
(Figure A1)
3. Hang a known weight; say 10 g, on the spring. Label the position indicated by the
marker on the white label as 10 g.
4. Repeat Step 3 for different slotted weights to obtain a weight scale on the label.
(Figure A2)
5. Use this device with weight scale to measure the weight of an object.
Figure A1
Figure A2
(According to Hooke’s Law, the extension of the spring in a spring balance is
proportional to the applied force. Thus the scale should have approximately equal
steps. The commercial spring balance works on this principle. The only difference is
that it is made small for convenience and it is already calibrated, i.e. it comes with a
weight scale.)