A Change of Direction-Exploring the Impact of Forces

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Objective

Students will be able to determine a way to change the direction of a moving object by conducting a simple experiment.

Big Idea

In this unit, students have been exploring speed and force. Now they get the opportunity to conduct an experiment to better understand how forces work.

Opening

5 minutes

To begin this lesson, I do a little demonstration with my students.  I visit the gym and borrow a field hockey stick and a small ball. I want the students to see a real-world application of the investigation that we are going to engage in.  The demonstration will also serve as a springboard for the students to make decisions about materials they will be using in the investigation. 

I gather the students together on the floor, leaving room to do the demonstration.  I say to the students, I have a hockey stick and a ball.  If I have someone stands here and holds the hockey stick, and I roll the ball so it hits the stick, do you know what will happen to the ball?  I solicit some answers from the students. 

I then say, I am going to have _____ stand here and hold the stick.  I am going to roll the ball toward the stick.  ____ is not going to move the stick.  The stick will be held still.  I want you to observe what happens to the ball.

I roll the ball with enough force that it hits the stick and changes direction.  I discuss with the students what they observed.  I then say to the students, do you think that anything that we put in front of the ball would cause it to change direction?  What would an object need to be like to cause the ball to change the direction? 

After the students share their ideas, I tell them to move to their stations and we will begin our experiment to see if we can figure out what types of things can cause a moving object to change direction.

 

Experiment

20 minutes

Supplies Needed:

For this part of the lesson, you will need one marble 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.  See Change of Direction Set Up Picture.  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 to provide a variety of objects for the students to choose from that they will use to try to get the marble that will be rolled down the track to change direction.  These objects should be ones that will cause the marble to change direction as well as ones that will not.  Some ideas for objects include books, folded paper, sponges, Legos, boxes, cotton balls, etc.  See Picture for the objects I used with my class. 

I provide the objects to scaffold this investigation.  The students are not quite ready to go into the classroom and pick out things to test on their own.  Pre-selecting the objects provide a framework for when the students will be making decisions of their for an investigation.  It also saves time!

You will also want to make copies of the A Change of Direction-Recording Sheet that is included as pdf with this lesson. 

Procedure:

I say to the students, Now it's time to see if you can figure out what object will cause a rolling marble to change direction.  We are going to make a prediction.  I want to look through the box and decide one thing that you think will cause a marble to change direction when rolled down a ramp.  I want you to draw a picture of the item you chose in the box on your recording sheet.  I give the students time to make their decision and draw a picture of it on their sheets.

After the students have made their predictions, I then give the students directions for how to conduct the experiment.  I say to the students, You are going to test each object from the box to see if it makes the marble change direction.  We will start with the sponge (or whatever object you want to have them start with).  I want you to place the sponge at the bottom of the track.  You will then put the marble at the top of the track and hold it in place with a pencil.  When I tell you to, I want you to lift the pencil and allow the marble to roll down the track.  I want you to observe the marble to see if it continues to move forward after it hits the sponge or if it changes direction. 

I tell the students to lift their pencils and allow the marble to roll down the ramp.  After they observe what happened, I tell the students who pick the sponge (if any) to record their results. We then continue the process, working through each of the objects and recording the results. See A Change of Direction Video.  Click to see samples of the students recording sheets:  A Student Work Sample 1  and Student Work Sample 2.

We then clean up and prepare for discussion.

 

 

Discussion

10 minutes

After the students complete the experiment, I ask them the follow questions to spark our discussion.

1.  What things caused the marble to change direction?  Which things did not?

2.  What did you notice about the objects that caused the marble to change direction? 

3.  Do you think it would make a difference if we moved the object farther away from the end of the ramp?

4.  What if we rolled something bigger down the ramp?  What if we rolled something like a bowling ball?  Would any of these objects cause the bowling ball to change direction?  What are some things that might be able to cause a bowling ball to change direction?

After the discussion, the students asked if they could try finding another object that would get the marble to change direction.  We actually did set up and I let the students try again (see reflection).