Scratch Computer Models & Simulations Level 3. What You’ll Learn… What is meant by models and simulations How models and simulations help us learn.

ScratchComputer Models & SimulationsLevel 3

What You’ll Learn… What is meant by models and simulations How models and simulations help us learn about real

world systems Advanced computer programming skills in Scratch How to use Scratch to model or simulate the behavior of a

system in the natural world

Stuff You’ll Need… Scratch Account

Evernote Suggestions… Write down three interesting things you learn every day. Keep a glossary of words you learn during these activities. Pay particular

attention to the bold, italicized words you find. Keep a list of all the ideas you have for your computer model. Explain how

you chose the system for your simulation. Describe the system you are modeling and the behaviors of objects within

that system. List any sources you used to research the system or behaviors of objects in

your computer simulation. Explain the purpose of the computer model that you created and what you

think the model will explain. If you simplified the behavior of any objects in your program, explain how

this might have affected your simulation. Take screen captures to record your progress in developing a computer

model or simulation with Scratch. Keep a record of any “bugs” in your program and how you fixed each bug.

What You Should Know…What you should already know

Be very familiar with creating and combining programming scripts to control Sprites

Be familiar with a wide variety of palettes and blocks and be able to learn the functions of those you have not yet used

Know how to find Scratch resources and project examples online

Know how to import images and sounds into Scratch Know where to find help or advice from other Scratch users Understand the program debugging process and how to

debug in Scratch

Before beginning this Learning Launcher, you should already be familiar with programming in Scratch. You should:

If you have been defeated by Level 3, perhaps you should revisit level 1 and 2 again?

What You Should Know…Models & Simulations

Ever since you were a youngster, you have used models to explore or understand the world around you. For example, growing up you may have had a stuffed animal toy, like a rabbit. The stuffed animal is not a real rabbit, but you used it to represent an actual rabbit. The toy rabbit is a model of a real rabbit.

What You Should Know…Models & SimulationsWe use models to explain or understand our world or complex situations. In science, a model of the solar system helps us to understand the position and movement of the planets around the Sun. In social studies, the globe models the location of countries on Earth. We use models when the actual object is too difficult, dangerous, or rare to use.

What You Should Know…

Like models, simulations help us to explore our world or test ideas. Computer models and computer simulations are similar. One difference between a model and a simulation is that, in simulations, the user may change or add information.

Often, computer models and simulations help us solve problems. They also allow us to test things safely or inexpensively.

This picture shows a computer image of a Ford Explorer crashing into a wall. Instead of

smashing real cars, the simulation allows us to smash virtual cars. We learn what happens in a car crash without having to risk a real crash

or smash a real car. Cheaper and safer!

Image: Courtesy of Oak Ridge National Laboratory

Computer Models & Simulations

What You Should Know…

Using a computer, we can predict events before they happen. The study of weather, meteorology, uses computer models or simulations to predict the weather.

In biology, simulations help us to predict relationships between different organisms. For example, we use computers to model changes in the number of predator and prey.

Image courtesy of the Department of Interior

Image courtesy U.S. Fish & Wildlife Service

Computer Models & Simulations

What You Should Know…

Making computer models that behave like objects or events in nature is challenging.

One of the hardest parts is making certain that we really understand what is happening.

The next set of slides is an example of a simple computer simulation in Scratch:

Modeling the behavior of a bouncing ball!

Computer Models & Simulations

Can you figure out the purpose of the

turn 3 degrees blocks?

What You Should Know…The Bouncy Ball Simulation

Now let’s take a closer look at the sprite’s programming. Notice there are two sets of blocks. The first set of blocks tells the ball to turn. The second set of blocks tells the ball to move 6 steps. If during those 6 steps the ball hits the edge of the stage, it is commanded to bounce.

Turn

Move & Bounce

Scratch contains a Sprite, called Bouncy Ball. The Bouncy Ball comes with a script that programs it to bounce across the stage.

Open Scratch, find the Bouncy Ball sprite (it’s in the “Things” folder) and watch its behavior. Do you think this is an accurate simulation of how a real ball would bounce? What behaviors seem accurate? What behaviors seem inaccurate?

What You Should Know…

Before we try to model the behavior of many balls, let’s make a list of how one ball behaves.

The Bouncy Ball SimulationHow can we use the Bouncy Ball sprite to show what happens when bouncing balls hit each other?

A single ball will:

Move in one direction forever or until something causes it to stop or change directionChange how it bounces if it hits or is hit by something elseFall toward the ground because of gravityEventually stop moving

This list is not complete! It’s just an example of some of

the ways a single ball behaves. Can you think of

any other behaviors we missed?

What You Should Know…How Do Two Balls Behave?Okay, we have our list for the behavior of a single bouncing ball.The Bouncy Ball sprite provides the blocks that programs one ball to bounce. What happens when we add more bouncing balls?

First, let’s add another Bouncy Ball sprite – we’ll call it ball2.

Next, we need to decide what to change about the blocks to make the balls bounce off each other. We know that if a ball hits another ball it must change direction and then move in that new direction.

The touching block (in the Sensing palette) allows the sprite to sense when it touches another object. Let’s use it to tell the first ball how to behave when it touches the second ball.

What You Should Know…How Do Several Balls Behave?

Here’s our new script to simulate two balls bouncing on the stage.

What is different about the one ball simulation and the two ball simulation? Is this an accurate simulation of how two balls would behave? Can you improve it?

Do It!

In the What You Should Know… section, we explored how to use Scratch to model the behavior of bouncing balls. Now it’s your turn to use Scratch to model or simulate the behavior of something in nature.

Think of a system in nature that you can model in Scratch. Identify the objects in your system. Make a list of behaviors for each object, including how they interact with other objects.

Create Your Own Model or Simulation

This can be a complex programming challenge!

We suggest that you choose a fairly simple system to

simulate.

It’s okay if you simplify certain behaviors of the objects in your

simulation.

Do It!

Need Ideas? Check out the example simulation projects in Scratch. Or go online to the official Scratch website and explore the work of other Scratch users.

Create Your Own Model or Simulation

A big advantage for programming in Scratch is the huge online user community! You can find lots of project ideas, tutorials, and helpful hints online. You can download other user’s projects and build upon their work. You can even post your own projects (the next slide will show you how)!

Go Online for Ideas, Help, Tutorials and to Share Projects

Check out the official MIT Scratch Site: http://scratch.mit.edu/ Browse the many great tutorials on YouTube (if you can’t access YouTube from

your SmartLab, you may have to do this from home) Explore the video tutorials at http://learnscratch.org/ Do an online search for other great Scratch resources and tutorials (HINT: Search

for “Scratch software” or Scratch MIT” to narrow your search)

Extend Yourself…

Scratch allows you to share your work with others who use Scratch.Steps: 1.Once you complete your project, select the Share menu. 2.Select, “Share This Project Online…”3.Complete the form and Click, “OK”.4.If you do not have an account, click on “Create account”.

a. Create account will take you to the Scratch website.

b. Select, “Signup” c. Return to Step #2.

Share Your Projects Online

Extend Yourself…

Extend Yourself… What other areas of research use computer simulations? What kinds of research are better

to simulate? Go online to learn more. How are simulations and games similar? How are they different? Think about those

questions and discuss it with your SmartLab partner or family. Learn more about simulations by visiting the website, PhET. Try to use their simulations. Create a simulation using a simple mathematical equation. For example, use Scratch to

draw a line across the stage. The equation for a line on a graph is y = mx + b. Study Newton’s Laws of Motion to learn more about how objects behave. Why do different scientists disagree so strongly about the effects of global warming? Go

online to learn more about how climatologists use models and simulations to predict climactic changes. What are some of the key variables they agree and disagree about and how does it affect their predictions?

Extend Yourself…

What if the bouncing ball represented something in nature, like a molecule?

In science we study the states of matter: solid, liquid, gas, and plasma.

The way that molecules behave in each state can be modeled with a computer. Can you figure out how?

The Bouncy Ball Molecule