Starting with my student's racetracks that they created in this lesson, today they will be using their racetracks to answer the question "Which objects work better when pushed? Which objects work better when pulled?" They will determine this by pushing and pulling objects around their racetracks and recording the time for each one. Then, they will use their data to create graphs to display the times which will lead into a conversation about the efficiency of push and pull forces. This lesson may take two class period to teach depending on how quickly students test their own objects.
I am teaching this lesson based on the Essential Standards, which is required by my state and I explain here, but is also an important concept to teach so students fully understand forces and motion. By students engaging in actually creating the motion, recording, and analyzing it, they will develop a clearer understanding of how changing the force can affect the speed of an object. I am also required to post an "I can..." statement for each lesson, and today's statement is "I can record data from push and pull forces and use it to create a graph".
We will use:
*Racetracks created in yesterday's lesson
*Stopwatch timers or digital timers on iPads (1 per student and 1 for the teacher)
*Printed data recording sheet for students to record data and then glue into their journals
*Variety of objects for students to push and pull around racetracks, including Matchbox cars, blocks, rocks, balls, cotton balls, etc.
*String and tape to allow students to pull objects that aren't naturally pulled.
Since my students have already had some experience with different motions in the introductory lesson and have created their own racetrack based on that knowledge, they are now ready to use the racetrack to discover the difference between what happens when you push and object and when you pull it. By the end of this lesson, students should be able to verbalize that some objects work better when they are pulled and some work better when they are pushed.
To get them started thinking about this, I want to model the process of asking a question and then conducting an investigation to figure out the answer. This supports the Science and Engineering Practices standards 1 and 3, by first determining what question to ask (SP1) and then conducting investigations to collect data which can be compared (SP3). SP3 includes making predictions about investigations which also occurs in this lesson.
First, I remind students that they designed and created a racetrack in order to test the push and pull forces of objects. I say,
"Yesterday, you all worked very hard to create a racetrack that we can use to test the push and pull forces of objects. You used lots of different motions to design it. What were some of the movements that you incorporated into your design? Can you give me the word and then show me the motion with your hands?"
I allow students to answer which movements they incorporated, like zig zag, straight, curved, etc. This is to review the motions and vocabulary words that we learned in the first lesson about forces and motion and to provide another review of what the motion means for any students that may still be learning new words.
After students have provided a list of the movements they used on their racetrack, I ask students to open their journals.
While the students created their racetracks in yesterday's lesson, they used some objects such as small cars, balls, marbles, and wooden blocks to modify their racetracks. Today, they are using the same objects to run their tests to collect data.
On a new page in our journal, I ask students to look at the objects I have collected that they can use in their investigations. I say,
"Look at these different objects. Some of you tried out different things yesterday on your racetracks and noticed that these objects move differently. Today, we are going to investigate those movements more closely. We are going to do one investigation together, then you are going to try 3 more on your own".
Since this is the first investigation we have done where students are collecting and recording data, I think it is important to model exactly how they use the stopwatches, move the objects by consistently starting and ending in the same place, and recording the data exactly. This lesson is occurring at the beginning of the school year so I plan to provide more guidance for students on how to do this process than I would towards the end of the school year when students are expected to construct their own investigations.
I use a racetrack and choose an object and begin by saying,
"I want to find out which objects work best by pulling and which objects work best by pushing. The question I am asking is, "Which objects work better by pulling and which objects work best by pushing?" To determine that, I am going to choose one object, like this block. Then, I am going to push the block from the 'start' box to the 'stop' box. I start my timer when I begin, and stop it when my object gets to the end of the track. I can only go fast enough that the block does not go off the racetrack. If it goes off the racetrack, I know I need to slow down. When I get to the 'stop' box, I can stop pushing it and write down how long it took. Watch me while I push it around the track."
I put the block on 'start' and tell the students that I am starting my stopwatch, then push the block through the racetrack. When I get to 'stop', I stop the stopwatch and say,
"It took me 12.2 seconds to push the block around the racetrack. I need to record my data. Look at the table I gave you and write down what I write down. On a table, columns go up and down. Find the column for 'Object' and write down 'Small wooden block'. Then, under the column for 'push', write down 12.2 seconds. Now I am ready to pull the block through the racetrack. How can I pull a block?"
For the students to pull the objects through the racetrack, they are going to attach a string using tape to each object. I anticipate that they say I can just drag the object around the track holding the front of it instead of pushing the back of it. Since that will change the data because they could drag any object at about the same speed and I want to make it more challenging so that they get different data when they pull different objects, I say,
"We are all going to try to pull objects the same way by taping a piece of string or yarn to the front of the object using tape. You can determine how long or short the string is for your objects".
Then, I cut a piece of string and tape it to the front of the block and put it on 'start', start my stopwatch, maneuver it through the racetrack, and press 'stop' when I get to the end. I say,
"It took 16.4 seconds to pull the block through the racetrack. We need to record that in the column for 'pull'. Now, the last column asks me to make a choice about which I thought was easier, pushing or pulling the block. What would you choose? Turn to a neighbor and tell them which motion you thought was easier for me with the block".
Since I am doing a lot of the talking in this lesson because I am modeling how to do the investigation, I want to provide some opportunities for students to talk to each other about what they are thinking, too. After about 30 seconds I say,
"Put your thumbs up if you thought it was easier when I pushed the block and put your thumbs down if you thought it was easier when I pulled it. I see most of you think it was easier when I pushed it. You're right! I got through the course faster when I pushed it, because it only took 12.2 seconds. It took 16.4 seconds when I pulled it which is a bigger number, so I know it took longer and was more difficult! Write 'push' in that column".
After students have watched me complete the investigation with a block, I quickly teach them how to use the timer on their iPads (a real stopwatch would be just fine).
Then, I ask students to choose a friend to work with on their own investigations. Sometimes I will choose partners for them and sometimes I let them choose their own. Since it is the beginning of the school year and some students have good friends from Kindergarten, I am still watching to see which partners work well together and who I need to separate for future projects. This is a pretty quick project so if students find out they do not work well together today I can talk to them afterwards about choosing a different partner next time.
I invite my students to choose 1 object to test from my collection and I say,
"Your partner can help you to remember all of the things you have to do, like starting the stopwatch right when you begin and then pressing 'stop' when you get to the end of the racetrack. Also, they can check and make sure you wrote down the time correctly. Then, you help them with theirs. When you are ready, do your first investigations and then show me what you did".
As students work, I walk around and help with the stopwatches, assist with taping the string for the 'pull' test, and make sure students are remembering to write down their data. After students finish with their first object I tell them to go and trade it for another one and test a different object. Depending on time, students may get to test 1-3 objects. If I feel that they need more time for this activity, I can extend a day and provide more time for testing and recording.
After students have tested 3 push and pull forces and recorded the data, I ask them to put their objects and racetracks away and join me on the carpet with their journals and a pencil. This may occur on the first day of the lesson, or this may serve as the introduction on the second day of this lesson.
Again, since students are beginning first graders, they have limited experience with graphing data other than whole group bar graphs in Kindergarten, so it is important that I model how to do this and not just expect that they can do it independently. Common Core State Standard 1.MD.C.4 states that students will "Organize, represent and interpret data with up to three categories" so after my example, they will graph three more objects. Since I am modeling exactly how they will graph their data and then supporting them as they graph, the layout of the graph is more complex than a simple bar graph. I say,
"We are going to graph my data from the tests with the wooden block first, then you are going to add your data to my data on your graph".
I distribute a blank graph that we use to graph our data on. I explain that at the bottom there is a place to write the name of the object and then a place to graph the time for the push and the pull. I write "wooden block" for Object 1, and say,
"To graph this accurately, which means correctly, I need to look back at my data chart and get the exact times for the push and the pull. Since 'push' is first on the graph, I will get my 'push' data first. Flip back your data chart and find the 'push' data for the wooden block. 12 seconds - so, I need to graph up to 12. I do that by putting my finger on 'push' at the bottom so I know I am in the right place, then going up to 12 and drawing a line across like this. Then, I color up to 12 lightly - I do it lightly so I can erase it if I make a mistake. This type of graph is called a bar graph because we are creating bars up to the numbers".
I repeat the process for the 'pull' data and then ask students to work with their partner to graph their data from their investigations. I walk around and help where students struggle or get confused. I also get my projector ready so I can show the student's graphs when they are done.
When everyone is done I say,
"Come back to the carpet with just your journal - leave your pencils at your table. That way, you can focus on the results without needing to change anything. Now, look at your table. Do you see some bars that are much higher than others? Who has one they would like to share?"
I use the Smart Board and document camera to project a student's journal and point out where the bars were higher and lower. I ask,
"What does it mean when a bar is higher?"
At this point, students need to articulate that a bar that is higher indicates that the number is higher, which means that it took the object longer to go around the racetrack.
I continue to use student's journals as examples, and engage the class in math talk. CCSS 1.MD.C.4 also states that students will "Ask and answer questions about the total number of of data points, how many in each category, and how many more or less are in one category than another". I ask the following questions:
How long did it take to push each object?
How long did it take to pull each object?
Did it take longer to push or pull this object?
Which object took less time to push?
Which object took less time to pull?
When we have finished a math talk about the data, I want to connect the lesson back to engineering and forces. I say,
"Scientists, including engineers and inventors, use data like this to help them design and build things to solve problems. Next week, we are going to solve a problem where you have to move a heavy load of bricks or sticks up a ramp to the top. Understanding how things move and which objects move better being pushed or pulled will help you with your design".
In this lesson, I am introducing students to collecting, recording, and graphing data with teacher support, so I will not do a formal 'grade' or assessment after this lesson. However, I do want to see who understands graphing and get a sense of who my high performers are with this skill.
I collect their journals and use my Science Journal Check in Sheet to record completion of the activity and also note who might need extra assistance, which I provide during our math small group mini-lessons just on the graphing standards.