Building a Racetrack to learn about Push and Pull Forces
Lesson 2 of 6
Objective: SWBAT design a racetrack to test push and pull forces of a variety of objects to determine which objects move faster when pushed versus pulled.
My students have already been introduced to lots of forces and motion vocabulary in this lesson. Now, they are going to use that vocabulary and their own background knowledge to design a racetrack that they can push and pull different objects along. Then, they will record the movements that the objects make on the track and the times it takes to pull different objects along it.
This lesson is aligned to Science Essential Standard 1.P.1.1, Explain the importance of a push or a pull to changing the motion of an object. Click here for my Explanation of Essential Standards and Essential Question. This lesson also aligns to Science and Engineering Practices 2 because students are developing a model (the racetrack) to represent patterns of movement in the natural and designed world. It also supports SEP 4 by providing an opportunity for students to record and share their observations, thoughts and ideas, and to use their knowledge of motion gained in the previous lesson to design their racetrack.
*A large piece of poster board or cardboard for each student or pair of students (clean, empty cereal boxes cut open along one edge and trimmed work really well)
*Pencils and markers
*A variety of things to use to form the outside bumper of the racetrack, such as paper towel tubes, egg cartons, tissue paper, stickers, sticks, foam, etc.
*Adhesives (Elmer's glue, glue sticks, Scotch tape, masking tape, etc.)
To get students really excited about designing and building their own racetrack, I show this video of a Hot Wheels racer, Tanner Foust, beating the world record for completing a 332 feet air jump. Then, I show this video of a really intense race car track.
Then I say,
"Today, you are going to create a racetrack! Let's get our journals ready and do some planning before we begin. Open up to a new page, write the date, and today's topic is 'Building a Racetrack'."
I write the same in my journal and I add a simple T Chart with 'Try it!' on one side and 'Do not try!' on the other. Then I refer back to the sorting chart we completed in yesterday's lesson where we determined whether each motion was caused by a push or a pull. I say,
"Let's think about the different motions we got from pushing and pulling objects. We need to consider those when we think about designing a track, because our design may cause us to push or pull and object differently which would change the motion. Which of these motions might we want our objects to do on our racetrack and which ones do we not want them to do? Let's make a list. I'll write in my journal and you write in yours".
I use the Forces and Motion table that we made yesterday to lead the conversation, and say things like,
"'Throw' is on this list. Am I going to be able to throw an object on the racetrack? No? Okay, let's put that in the 'Do not try!' column. How about 'zig zag'? Can an object be pulled or pushed in a zig zag on my racetrack? I think that might work, so I'll put in in the 'Try it!' column. Can you think of any other motions you want to try with your objects on the racetrack that are not on this list?"
I include the last question because the list of vocabulary that I used in the previous lesson was not comprehensive and I want students to continue to grow their own lists. After I have about 8-10 different words on my list, I tell students to keep their journal with them so they can remember what they want to try, and to get a piece of poster board and a pencil.
The warm up to this lesson focuses on objective W.1.8, where students are recalling information from experiences and gathering information to answer questions. This activity with the T chart, referencing yesterday's vocabulary word sort and talking about what we could try and what we do not think will work allows students the opportunity to think about the experiences they had with those vocabulary words and objects yesterday and predict whether they will work with a different object for this project.
For students to really understand force as an interaction of two objects and motion as the outcome of a push or a pull force, they are going to create a racetrack. They will use the track in the next lesson to record the time it takes for them to push or pull different objects from the start to the finish.
First, I say,
"Today you are going to make a racetrack and then you are going to measure how long it takes you to push or pull different objects along your track".
Students will use the poster board/cardboard piece to first design a road that their objects will travel on. They are working independently today for two reasons. For one, I anticipate them wanting to take their own racetrack home when we have finished the project. Also, I want to have enough different tracks that the students can try a variety of different movements on them. The more racetracks they make, the more experiences they will have. I say,
"To design your racetrack, pick a starting place on one side of the cardboard and draw a small square and write 'start'. That is where you will place your object when you are ready to test your course. Then, you are going to carefully draw a road to the other side of the cardboard. You want it to be an interesting racetrack, so include lots of different turns and twists! Then, when your road ends up at the other side of the poster board, draw another square and write 'finish'. Use a pencil first, and then let me know and I will look at it before you trace the lines with a marker. Any questions? Watch me start mine, then you can begin.'
As students work, I walk around and ask question to get students to think about what their design will cause them to do when they are pulling or pushing an object along it. Since many students have already had experiences especially with toy cars on racetracks, I want to
On my own example board, I draw a small square, write 'start', and begin to draw a road. I want to avoid students copying my ideas, so I only draw a few inches then stop, and then I tell them to begin.
As students draw their racetracks, I talk to them and ask about their track, saying things like, "What do you think will happen when you push a car around this corner?" and "How do you think an object will react when you pull it on this section?" I want to get students to start predicting the reaction of objects when push and pull forces are applied. Some students may not be able to predict those just yet, so when students start to finish the pencil drawn racetrack I say,
"Okay, everybody. Now that you have your racetrack drawn with pencil, take one object and try to push it around your track. Then, put it back on 'start' and pull it around your track. If you cannot pull it, we have string and tape and we can turn it into something you can pull. While you are trying this, think about whether or not you need to change your track. It might be too easy or to hard for the objects. You can erase the pencil lines you drew and redraw them if you need to".
I help students to turn objects into ones they can pull and continue to ask students about how the objects are responding on the racetrack by saying things like, "Can you get your object to move faster? What happens if you really slow down on that curve?"
By engaging students in thinking about speed at this point, they can try different objects and discover that they get different outcomes when they pull or push an object at different speeds. After a few minutes, I stop the class again and tell them,
"When you are ready, use a marker to outline the edges of your racetrack. Using a marker makes the lines permanent, so make sure that it is just the way you want it first. After you have traced the lines all the way across, you can use our recycle supply box to build things along the sides of your racetrack or to decorate it while everyone else finishes up. Then we'll race them tomorrow!"
Some students will naturally work more quickly than others, so once they are finished designing they can spend time decorating their tracks. The students who work more slowly can have additional time during other parts of the day to finish adding decorations (like houses, barns, stores, parks, trees, etc.) to the track. I purposefully do not mention how students can decorate their racetracks because that part does not matter so much instructionally, so I feel comfortable allowing more freedom with that part.
The designing and building of the track takes most of an entire lesson, so after about 20-25 minutes I say,
"Take about 2 minutes and finish what you can for today. Then we'll try to finish them in the morning and tomorrow we will race our tracks with different objects using push and pull forces. For now, put your supplies away and meet me with your Science Journal on the carpet".
To connect the activity of building the racetrack back to the standards of understanding push and pull forces, the discussion is important and needs to focus the students back on the vocabulary that we started with. This supports writing standard W. 1.7, because students are participating in shared research through this conversation based on their experiences. I say,
"Look at your T chart and the movements you wanted to try to get your object to make on the track. What did you notice when you practiced pulling and pushing the objects along your track?"
Then, I listed to the discussion. Through this discussion, I want to hear that students are realizing that some movements are more likely to occur when objects are pushed, and some when they are pulled. Also, I want students to verbalize that they have different amounts of control over objects depending on the object, whether they are pushing or pulling, and the speed they apply. I ask probing questions to get students thinking about these things, like 'Did you notice anything change if you went really fast? Did anybody try to pull really slowly? Were some objects easier to control than others? Why do you think that might be?'
After a few minutes, I tell students that tomorrow we will collect and record data from races on our racetracks and I collect the journals for safe keeping.