Stop It!-Exploring Forces on Moving Objects

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Students will be able to explain what is needed to stop an object by completing a simple investigation.

Big Idea

This unit has allowed the students to explore objects in motion. Now it's time to figure out how to make them stop!


10 minutes

To begin the lesson, I begin with a short demonstration/conversation.  I set up a "Hot Wheels" track from a table to the floor and I invite the students to gather around the track.  I have a car to roll down the track.

I say to the students, In our last few science lessons, we have been rolling cars down tracks just like this (I let go of the car on the track and allow it to roll down).  I am wondering...if I wanted the car to stop at the bottom of the track without me touching it, what would I need to do?  I solicit answers from the students.  I build the discussion off of responses that say we could put something at the bottom of the track.

If we were to put something at the bottom of the track to stop the car, would it matter how big it is?, we are going to explore just that, so let's move to our stations and begin our investigation!


20 minutes

Supplies Needed:

For this part of the lesson, you will need one Matchbox type car for each group.   for each group of students. You will also need something that can be used as a track.  A length of board (like a 2" x 4" that can reach from the edge of a table to the floor for each group or a set of "Hot Wheels" track that will reach from the floor to the table for each group.    Eight inches away from the end of the track, place a strip of tape on the floor so the students know where to set the objects they will be using to get the marble to change direction. 

You will also need the Will It Stop the Car Investigation Recording Sheet that is included as a PDF with the lesson.  You will need the objects on the sheet for each group:  A folded piece of construction paper, a cotton ball, a book, a sponge, and a block.  I put the items in a tray for each table. 


I say to the students, We are going to test items to see if they will stop the car at the bottom of the race track.  This is called conducting an investigation.  Before we test each item, we are going to make a prediction just like scientists do.  I want you to lift  and touch each item in the tray.  Make a prediction.  Do you think the item will stop the car.  If you think it will, circle yes.  If you do not think it will, circle no.

I give the students time to go through each object and record their predictions on the recording sheet.  Once the students are done, we begin the investigation.  We do each test together so everyone sees the results at the same time.  The students record their results on their recording sheet (See Work Sample).

We start with the folded piece of paper and work through each object.  There is a lot of excitement in the room (see Video). During the investigation, I circulate to different tables and engage the students in a conversation about the item they selected and the prediction that they have made.  I am trying to lead the students to draw a conclusion about what it takes to stop the object (see Video). After we have tested all of the items, we clean up and come together for discussion.


10 minutes

To wrap up the lesson, we discuss the findings of our investigation to help the students draw some conclusions.  I ask the following questions:

1.  What objects were able to stop the cars? 

2.  Why do you think they were able to stop the cars?

3.  Can we make a conclusion about what type of object was needed to stop the cars?

4.  Can you think of some other things that we could put at the end of the ramp that might stop the cars?

5.  When we put the cars on the track some things stopped them.  What if we rolled a marble down the track instead of a car.  What if we put something in front of the marble.  Would it stop or would something else happen?  I want you to think about that, because we are going to explore that idea some more tomorrow!