This lesson aligns to Essential Standard 1.P.1.1, 'Explain the importance of a push or pull to changing the motion of an object". The purpose of this lesson is to provide students with the understanding that the force needed to push or pull an object changes--increase or decreases--if the weight of the object changes. It is important for students to understand this in order to really understand force, because then they will understand why sometimes they can push open a door with ease--and sometimes they cannot! In North Carolina, we teach the Science Essential Standards. Click here to hear more.
*Lots of tubs (I use plastic shoe boxes that can be pushed and pulled easily on carpet/desks)
*Classroom objects of different weights - the students can get these/put them back as needed - books work well!
To get started, I say,
"Turn to a neighbor and take 2 minutes to write a list in your journals of all the things that are hard for kids to push".
Then I ask my students to share and I write their ideas on the board. We repeat the activities with things that are hard for kids to pull, and I write those ideas on the board. Then I say,
"Why do you think some things are hard to push or pull, and some are not?"
I give my students a few minutes to think and talk about this so that I can hear if any of them already have ideas about weight or friction playing a part in this! When they have given some ideas, we move into the activity.
Since my students have already done a few different investigations with pushing and pulling, it is time for them to try to develop their own investigation! I say,
"How could you test this idea of the weight changing how hard it is to push or pull an object?"
Although I am not ready to let my students just go freely and do this on their own, I guide them through the process towards an investigation that (I think!) will get them some good information to answer the question. Planning and carrying out investigations with guidance to produce data to serve as the basis for evidence to answer a question in first grade aligns to Science and Engineering Practice 3.
As students give their ideas, I remind them of 'limits'--things that we cannot change, like time constraints, or things we simply do not have. We finally settle on using small boxes from around the room and different objects of differing weights that they can push, change weight, push again, and compare. (Surprise! This was what I had in mind all along...but they didn't need to know!!) Then, I ask the big question before we get started:
"Okay, investigators...how are you going to record your data today?"
I can imagine leaving it up to them - although I have really tried to make an effort at teaching them how to organize data into tables or graphs, they are not quite there yet, either--and that's okay! But, I want to know that they think about it before they start the investigation, at least with some sort of T-chart comparison ready to use. After our discussion, they begin their investigation and I help them where I am needed.
After about 15 minutes, I say,
"Make sure you have investigated both pushes and pulls, and tried different weights! We will stop in about 3 minutes and discuss your findings!"
In 3 minutes, we stop, clean up, and meet on the carpet.
To discuss what the students find, I want them to do the talking but I take notes on the board or the anchor chart. If I hear them making an important connection, like "The heavier the load got, the harder it was to push!" then I write it down.
Sharing ideas and communicating information from experiences and investigations supports Science and Engineering Practice 8 and using drawings and writings from the observations and investigations supports practice 4.
After everyone gets to share, I say,
"It sounds like we made some very important scientific discoveries today. The heavier a load is, the harder it is to push and pull it. The lighter a load is, the easier it is to push and pull it. Do you know what scientists and people did when they realized this a long time ago? They invented other tools to move things that were really heavy, like levels and pulleys and wheels! That way, they could move the heavy objects more easily!"
Although in first grade we do not really get into other tools, I have some books in our classroom library with pulley and levers and I share those with the class and suggest the students look at them if they are interested, which continues their learning in the subject even after the lesson!