Grade 8 – Structures & Mechanisms

Lesson Summary: Students will create an interactive simulation that demonstrates mechanical advantage.

Curriculum Expectations: These expectations are intended to highlight the many ways in which this lesson could support

the curriculum. It is neither expected nor necessary for teachers to address all of these expectations at once. Teachers

are encouraged to select the most relevant expectations based on their unique context and intentions for the lesson.

Science & Technology

Mathematics

Language - Writing

Overall Expectations

A2. use coding in investigations and

to model concepts, and assess the

impact of coding and of emerging

technologies on everyday life and in

STEM-related fields

A3. demonstrate an understanding of

the practical applications of science

and technology, and of contributions

to science and technology from

people with diverse lived experiences

D2. demonstrate an understanding of

different types of systems and the

factors that contribute to their safe

and efficient operation

Specific Expectations

A2.1 write and execute code in

investigations and when modelling

concepts, with a focus on automating

large systems in action

A2.2 identify and describe impacts of

coding and of emerging technologies,

such as artificial intelligence systems,

on everyday life, including skilled

trades

A3.3 analyse contributions to science

and technology from various

communities

D2.4 use the scientific

terms displacement, force, work, ener

gy, and efficiency to describe

everyday experiences

D2.5 demonstrate an understanding

of the relationships between work,

force, and displacement in simple

systems

D2.6 explain the relationship

between input and output forces and

determine the mechanical advantage

of various mechanical systems,

including simple machines

Overall Expectations

C3. solve problems and create

computational representations of

mathematical situations using coding

concepts and skills

Specific Expectations

C3.1 solve problems and create

computational representations of

mathematical situations by writing

and executing code including

code that involves the analysis of

data in order to inform and

communicate decisions

C3.2 read and alter existing code

involving the analysis of data in order

to inform and communicate

decisions, and describe how changes

to the code affect the outcomes and

the efficiency of the code

Overall Expectations

1. Generate, gather, and organize

ideas and information to write for an

intended purpose and audience

2. draft and revise their writing, using

a variety of informational, literary,

and graphic forms and stylistic

elements appropriate for the purpose

and audience;

Specific Expectations

1.1 identify the topic, purpose,

audience, and form for writing

1.2 generate ideas about a potential

topic, using a variety of strategies and

resources

1.3 gather information to support

ideas for writing in a variety of ways

and/or from a variety of sources

1.4 sort ideas and information for

their writing in a variety of ways

2.1 write short texts using a variety of

forms

2.3 use words and phrases that will

help convey their meaning as

specifically as possible

2.4 vary sentence structures and

maintain continuity by using joining

words (e.g., and, or) to combine

simple sentences and using words

that indicate time and sequence to

link sentences

3.4 use punctuation to help

communicate their intended

meaning, with a focus on the use of:

quotation marks to indicate direct

speech; commas to mark

grammatical boundaries within

sentences; capital letters and final

punctuation to mark the beginning

and end of sentences

3.8 produce pieces of published work

to meet identified criteria based on

the expectations related to content,

organization, style, use of

conventions, and use of presentation

strategies

Breaking Down the Coding Expectations in Science & Technology:

In the Grade 8 Science & Technology curriculum, there are 2 coding related expectations:

A2.1 write and execute code in investigations and when modelling concepts, with a focus on automating large

systems in action

A2.2 identify and describe impacts of coding and of emerging technologies, such as artificial intelligence

systems, on everyday life, including skilled trades

To paraphrase these expectations and express them in plainer language, students are being asked to:

● write code to demonstrate a science-related concept, focusing on writing code that includes elements of

automation

● show how coding impacts our lives

Both expectations will be addressed through the project.

Learning Goals: We are learning to write code to create an interactive simulation that demonstrates mechanical

advantage.

Success Criteria:

1. I can use conditionals to respond to data in my code

2. I can use user input to influence the progression of my code

3. I can use variables to store and process data in my code

4. I can represent the relationship between input and output forces on mechanical advantage

STEM Profile:

A systems engineer is someone who studies and designs how to design, integrate

and manage complex systems. This is used across many different fields, but is

commonly used in aerospace engineering.

Ave Kludze is a Ghanaian-American who is a senior Spacecraft Systems Engineer

at NASA. Although he never achieved his childhood dream of becoming a pilot,

he is now developing and flying spacecraft for NASA using his knowledge of

complex systems. Lovingly known as “Africa’s Rocket Man”, he wants to share

his childhood love of science with more youth across the African continent.

Like Ave, we will be exploring systems in action to better understand how they

work and what forces are at play. Let’s get started!

Minds On:

1. Students will have different experience levels when it comes to coding.

a) If students have never experienced coding before, please watch the “What is Coding?” video.

b) If students have experienced coding before, have a quick discussion in which students share their definition

of coding. Some responses to look for include:

i. Coding is the language that computers speak

ii. Coding is how we talk to computers or get computers to do what we want

iii. Coding is the instructions that we give to a computer

2. In small groups or as a whole class, brainstorm with students to generate ideas and key concepts that should be

represented in their simulation. Some sample prompts include:

o What is force? What is mechanical advantage?

o How are force and mechanical advantage at play in a simple machine like a lever?

o How does the location of the fulcrum affect the forces and mechanical advantage in a lever?

 
Planning Our Project:  
 
Introduce  the idea  of  a  flowchart,  a  type of diagram that  shows the  sequence  of steps involved  in  performing  an 
algorithm, with specific symbols used to represent different control structures. The symbols used in a flowchart are: 
  
•  Oval - used to show the beginning and end of the program 
•  Parallelogram - used to represent input or output 
•  Rectangle - used to show processing (i.e., calculating or 
manipulating data)  
•  Diamond - used to show decisions (i.e., conditionals) 
•  Lines and arrows - used to connect the shapes to show the 
direction of the steps and to represent loops 
•  Text and labels - included with shapes, as necessary.  
 
Since every student’s project will be different, so will the flowcharts that they 
create and the tools or technologies from which they can choose to create 
their  flowcharts  (i.e.,  pen  and  paper,  dedicated  apps  and  websites  for 
creating flowcharts). A sample flowchart has been provided below to give a 
general sense of what the end product may look like.  
 
Creating Our Project: 
 
The sample code demonstrate how the project might work and please note that there is code written in all three sprites 
and the stage. For your reference, Scratch determines where to display sprites and controls movement using a Cartesian 
coordinate system, with (0,0) being the center of the screen and it may be helpful to pre-teach this concept, if it is one 
with which students are unfamiliar.  
 
Part 1: Create the Title Screen & Start Button 
 
1.  Create a backdrop using the paint editor that will serve as a title slide with instructions on how the simulation will 
work (i.e. to press the spacebar to test if the mechanical advantage is sufficient to lift the object). Also create a 
blank backdrop that will be used after the start screen.  
 
2.  In the stage, use the When Green Flag Clicked block and the Switch Backdrop To () block to ensure that at the start 
of the simulation users always begin on the title slide.  
 
3.  Delete the default Cat sprite and create a new sprite that will serve as the start button for the game. You can: 
a.  Use the “Choose a Sprite” option and select one of the pre-designed button sprites available in Scratch. 
b.  Upon adding the sprite, edit the costume of that sprite using the text tool to add a word or phrase like “Start”. 
 
4.  In the code for the start button, use the When Green Flag Clicked block and the Show block so that the button will 
always appear at the start of the simulation.  
 
5.  Still in the code for the start button, add the When This Sprite Clicked event block, the Switch Backdrop To () block, 
and the Hide block. Set the Switch Backdrop To () block to match the name of your blank backdrop. This will make 
it so that clicking the start button will cause the simulation to advance and the start button to disappear once the 
simulation begins.  
 
Part 2: Create the Lever/Object to Be Lifted and the Fulcrum 
 
1.  Create a custom sprite using the paint editor that will serve as both the lever and the object to be lifted.  Use the 
rectangle tool to create a long, thin rectangle that will cover most of the screen. Add some kind of object near the 
right-hand side of the rectangle to serve as the object that will appear to be lifted.  
 
2.  Use the pre-designed Ball sprite available within Scratch to serve as the fulcrum. Resize the sprite in the Sprite Pane 
if necessary to compliment the size of your lever sprite.  
 

Part 3: Create the Variables 
 
1.  Create 4 new variables in the orange Variables menu, named: Force In, Force Out, Fulcrum Location, and Mechanical 
Advantage, and deselect the checkbox next to the Force Out variable so it does not appear on screen. 
 
2.  Right click on the Force In and Fulcrum Location variables as they appear on the stage and change them both to a 
sliding variable. The Mechanical Advantage variable should NOT be changed to a slider.  
 
3.  Right click on the Fulcrum Location variable again to change the slider range. 
a.  The range will need to be set depending on the length of the “lever” you created in Part 2.  
b.  You can click and drag the Fulcrum sprite to determine the coordinates of each end of the lever.  
c.  To make the simulation look more realistic, your Fulcrum Location variable should be set to 10 less than 
the  X  coordinates  of  each  end  of  the  lever  (i.e.,  in  the  sample  code  provided,  the  lever  ends  are  at 
approximately -180 and 180, so the Fulcrum Location slider range is set to -170 and 170).  
 
Part 4: Set the Variable Values 
 
1.  In the stage, add a Forever loop under the Switch Backdrop To () block that should already be there from Part 1. 
The next steps should all be inside of that loop.  
 
2.  To allow the fulcrum to move almost to the end of the lever (but not quite), as well as to compare the input and 
output lengths of the lever to determine mechanical advantage, use a Set () to () block from the orange variables 
menu and set the variable name to Mechanical Advantage.  
a.  In the blank space, add a () / () block.  
b.  In the first and second blank space of the () / () block, add () + ()  and a () – () blocks, respectively.  
c.  In the () + () block, add the block for the Fulcrum Location variable into the first blank space. Type the 
number 175 in the second blank space.  
d.  In the () – () block, type the number 175 in the first blank space. Add the Fulcrum Location variable in the 
second blank space. 
e.  You should end up with the statement: Set Mechanical Advantage to (Fulcrum Location) + 175 / 175  - 
(Fulcrum Location) 
f.  The numbers 175 and -175 were used based on both the length of the level sprite in the sample code and 
the fact that the Fulcrum Location variable has a maximum range of -170 and 170. You may need to adjust 
these numbers based on the size of the sprites in your own project.  
 
3.  Use another Set () to () block from the orange variables menu and set the variable name to Force Out.  
a.  Inside the blank space add a () * () block 
b.  Add the block for the Mechanical Advantage variable in the first blank space. 
c.  Add the block for the Force In variable in the second blank space. 
d.  You should end up with the statement: Set Force Out to Mechanical Advantage & Force In 
e.  This section will determine the output force based on the input force chosen by the user with the variable 
slider and the mechanical advantage calculated in the previous step.  
 
Part 5: Program the Fulcrum 
 
1.  To make it so that changing the value of the Fulcrum Location variable, using the slider, will cause the actual fulcrum 
sprite to move accordingly, add a When Green Flag Clicked block and place a Hide block underneath to ensure that 
the sprite does not appear on screen during the title slide. 
 
2.  Add a When Backdrop Switches To () block and set it to the name of your blank backdrop. 
 
3.  Add a Show block and a Forever block. 
 
4.  Inside the Forever block, add a Go To X () Y () block.  
a.  Set the X coordinate to the Fulcrum Location variable. 
b.  Set the Y value to a coordinate that is underneath your lever sprite so that it still appears to be touching 
the lever (i.e., in the sample code, this value is -100). 

 
Part 6: Program the Lever & Object 
 
1.  Add a When Green Flag Clicked block and place a Hide block underneath to ensure that the sprite does not appear 
on screen during the title slide. 
 
2.  Add a When Backdrop Switches To () block and set it to the name of your blank backdrop. 
 
3.  Add a Show block and a Go To X () Y () block. Set the coordinates to the desired position of your sprite. In the sample 
code, this is Go To X (0) Y (-35). 
 
4.  Add a Point in Direction block and set to 90.  
   
Part 7A: Check if Enough Mechanical Advantage (cont’d from part 6) 
 
1.  To allow the user to continuously change the values of the Force In and Fulcrum Location variables, add a Forever 
block. 
2.  To provide users with enough time to adjust the sliders for the variables and then check to see if there is sufficient 
mechanical advantage, add an If () Then block inside of the Forever block. 
3.  Inside the blank space to declare the condition, add a Key () Pressed? Block (i.e., In the sample code, this is set to 
evaluate if the space key is being pressed) 
4.  All subsequent code will be inside of this block.  
   
Part 7B: Not Enough Mechanical Advantage 
 
1.  Add an If () Then Else block. Inside the blank space to declare the condition, add a () < () block.  
a.  Fill the first blank space with the Force Out variable  
b.  Set the second blank space to a number of your choosing. This is the “weight” that we are assigning to the 
object being lifted by the lever and will be used to determine whether or not the object will be lifted based 
on the Force In and Fulcrum Location variable values being set by the user and the calculated mechanical 
advantage (i.e., in the sample code, this number is set to 150)  
 
2.  Inside of the If Then section of the If () Then Else block from the previous step: 
a.  Add a Point in Direction block and set it to 90.  
b.  Add a Say () for () Seconds block. Write a message telling the user that they do not have enough mechanical 
advantage to lift the object and to try again.  
 
Part 7C: Enough Mechanical Advantage 
 
1.  Inside of the Else section of the If () Then Else block from Part 7B, Step 8:  
a.  Add a Turn Left () Degrees block. Set it to approximately 15 degrees.  
b.  Add a Change Y By () block and add a () / () block inside of the blank space.  
i.  Set the first blank space of the () / () block to the Fulcrum Location variable.  
ii.  Set the second blank space to -4. 
iii.  You should end up with a block that reads: Change Y By Fulcrum Location / -4.  
iv.  This block will cause the lever to appear to “lift” if sufficient mechanical advantage is available. By 
setting the change in position relevant to the value of the Fulcrum Location, it will ensure that the 
lever sprite does not appear to ‘float’ above the Fulcrum sprite. You may need to adjust these 
numbers to find the right fit for your project (i.e., a smaller negative number such as -2, -3, -4) 
c.  Add  a  Say  ()  for  ()  Seconds  block  and  write  a  message  congratulating  the  user  for  having  sufficient 
mechanical advantage to lift the object.  
d.  Add a Turn Right () Degrees and set it to the same value you used in Step 10A (i.e., 15 in this example).  
e.  Add the same block from Step 10B, but change the final value to the same number but as a positive integer 
(i.e., if -4 was used, then this value should be +4). You should end up with a block that reads: Change Y by 
Fulcrum Location / +4.  
f.  These final two blocks will ensure that the lever goes back down to its original state after the successful 
message has appeared on screen so that the user can continue to use the simulator without having to 
restart the code.  

Extensions 
 
●  Investigate how changing the “weight” assigned to the object in Part 7B, Step 8 affects how the code will run. 
●  Add another sprite to simulate the effect of a person “pushing down” on the lever.  
●  Consider adding sound effects to the simulation using the pre-loaded sounds in Scratch or use the Sound Editor 
to record their own sounds. The Start Sound () and Play Sound () Until Done blocks will allow students to insert 
those files into their code.  
●  To learn more about Abe Kludze and force and mechanical advantage, consider the following books and videos: 
o  Ave Kludze, Ghanaian rocket scientist at NASA from Minister Faust 
o  Bill Nye and Mechanical Advantage from GeorgeBuford 
o  mechanical advantage explained (lever, block and tackle, inclined plane) from cg-physics-global 
o  The mighty mathematics of the lever - Andy Peterson and Zack Patterson from TED-Ed 
 
Sharing Our Work/Consolidation: Students can share Scratch projects using these steps.  
 
1.  Students  should  be  provided  with  time  to  share  their  projects  with  others  and  to  engage  in  self  and  peer 
assessment. This can be done in a variety of different formats, including a gallery walk, whole class presentation, or 
“trading” their project with another student. Students can provide feedback in a variety of ways, including written 
and verbal. A variety of feedback options and templates are available in Appendix A. 
 
2.  An important aspect of assessing student understanding is focusing on the process, not the product. While it is 
important to have a final product that functions as intended, students are often asked to produce something within 
a limited time frame; therefore, it may be the case that, given more time, a student would be able to produce a 
fully functional product.  
 
To assess learning,  teachers  can  conference with  students  throughout  the  creation  of  their  projects  using the 
anecdotal  prompts  in  Appendix  B  and  documenting  these  discussions  using  an  anecdotal  observations  chart. 
Teachers are encouraged to consider the troubleshooting strategies used by students throughout the project, their 
ability to explain how their project works, and what they might do differently in the future.   
 
3.  A rubric can be used to evaluate the final product. This and other assessment and evaluation tools can be modified, 
as needed. 
 
Low -Tech/No-Tech Modifications:  
 
●  While it is ideal to have one device per student, this is not the reality for many classrooms. If you are planning to 
have students work in groups, consider a maximum group size of 2 students to ensure as much “hands-on” time 
with coding as possible. If access to devices is limited, you may wish to implement this lesson as part of a station 
rotation within your classroom or use another strategy to work with small groups.  
●  If you have no access to devices, you can: 
o  print images of the Scratch blocks in the folder at this link, cut them out and have students create their 
code with paper blocks instead. 
o  You may also wish to print out images of the background scenes and characters to further support students 
 
Appendix A: Self and Peer Feedback 
 
•  Student Self Assessment 
o  Thumbs Up 
o  WIN  
•  Peer Assessment 
o  Two Stars and a Wish 
o  TAG  
 
 
 
 
 
 

Appendix B: Anecdotal Prompts

Throughout the time when students are creating their projects, teachers are encouraged to circulate and conference

with students to discuss their projects and progress. The process is just as, if not more, important than the final product

when it comes to coding, so this is key to truly understanding a student's understanding.

Key Concepts

Students should be able to identify, name, and explain key coding concepts in their own words; for example, sequence

can be described as “the order in which you write your code matters”. Conditionals can be described as “if-then

statements that give your computer options to choose from.” The wording may be unique to each student, but they

should be able to explain the concept.

Suggested Prompts:

1. Can you tell me what you know about ______?

2. Can you show me where in your code you used _____? How does it work?

Application

There may be times when students “stumble” into the “right” answer in their code without fully understanding how

they got there, while another student may have a project that isn’t working the way they intend, but they know exactly

why and are able to very clearly articulate the steps they would take to fix the issue, if they had more time. Just because

a student’s project is not working exactly as they want it does not necessarily mean that they don’t understand so it is

important to take the time to discuss with students.

Suggested Prompts:

1. Can you tell me what this section of your code does?

2. It seems like this section of code isn’t working the way you want it to. Why do you think that might be? How

might you fix it?

3. What would happen if you made _____ change?

Troubleshooting/Debugging

In the world of code, a lot of mistakes are going to be made. Not only is this completely normal (and it happens to

professional computer programmers all the time), but it is actually HOW we learn to code. To move from making the

mistake into learning from it, students need to develop and utilize effective troubleshooting strategies. If a student just

sits there staring at their code for a week trying to figure out an issue without ever asking for help, they are not

demonstrating effective troubleshooting strategies. Effective troubleshooting strategies that students may demonstrate

include:

● Reading their code out loud to themselves to attempt to identify errors

● Sharing their code with a peer to ask for help in identifying an error

● Dealing with frustration by taking a break from their code

● Searching the web for answers to their questions

Suggested Prompts:

1. Can you tell me about a time where your code wasn’t working the way you wanted it to? What did you do to

fix it?

2. It seems like this section of code isn’t working the way you want it to. Why do you think that might be? How

might you fix it?

3. What are some mistakes you made when creating your project? What would you do differently next time?