# Which One Is Faster?- An Introductory Investigation of Speed

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## Objective

Students will be able to determine which vehicle travels faster by conducting an investigation.

#### Big Idea

In this unit, students have been exploring the speed of animals. Now, this exploration of speed switches to non-living things as the students compare the speeds of toy cars.

## Opening

10 minutes

The previous two lessons in this unit have focused on the speed of different animals.  The book Fast, Faster, Fastest-Animals that Move at Great Speeds which is available on Amazon.  If you have not read this story, you can read it as a springboard for the conversation that will take place.  If you have already read it, you can just reference it as you are talking to the students.

I gather the students in front of my big chair and I say to them, We have been talking a lot about how fast different animals are.  I wonder, how do the scientists know how fast these animals are?

This question leads to a discussion about stopwatches, timers, radar and more.  I then ask the students, What if we didn't have any of that of equipment?  How could we find out which animals were the fastest without using special equipment?  Hopefully, the students come up with the idea of some type of comparison or race.  This discussion will then lead into the introduction of the next section of the lesson.

## Investigation

15 minutes

For this part of the lesson, you will need two "Matchbox" type cars for each group of students. The cars should not be identical.   Label one car of each set "A" and the other car "B" using masking tape.  You will also need something that can be used as a track for comparing the speeds of the two cars.  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 two sets of "Hot Wheels" track that will reach from the floor to the table for each group.  Click here to see experiment set up.

You will also want copies of the simple Investigation Recording Sheet that is included as a PDF with this lesson.  There are two copies per sheet.  I distribute the sheet to the students and have them write their names on

I say to the students, we are going to find out which car is the fastest of the two cars your group has.  Two do that, you are going to conduct an investigation,  But, before we conduct our investigation, we are going to make a prediction about which car will be the fastest.  Remember, a prediction is a really good guess.  So I want you to look at the cars, hold them, compare them and decide which one will be fastest.  Then on your sheet, I want you to circle that car.  If you think it will be Car A, circle the A car on your sheet.  If you think it will be Car B, circle the B car on your sheet.

We then discuss how we will make sure that the variables are controlled during our experiment.  For the controls, we talk about how the cars cannot be pushed down the track.  I show them how to use a pencil to hold the cars in place and then lift the pencil to start the cars down the track. Click here to see example. We also talk about how we cannot change the position of the track.   The two cars that we are racing are different.  We do not get into a big discussion about how they are different because we will be talking about this in subsequent lessons.

We also talk about how we should probably try racing the cars more than once to make sure our results are accurate.  We decide on best two out of three.

The students conduct the experiment (see video) and record their results when they are done.  The results go on the bottom of their prediction sheet.  We then clean up and gather together for discussion.

## Discussion

10 minutes

After all the work setting up the experiment and running, it is easy to forget about bringing closure to the lesson.  The discussion that I have with the students is likely the most important part of this lesson.  It helps to direct their scientific thinking and to build background for future lessons in this unit.

We gather together to discuss the students findings.  I ask the students some questions about the experiment.