Which One Is the Fastest?-A Continuing Investigation of Speed

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Students will be able determine which toy car is the fastest by conducting a simple investigation.

Big Idea

In the previous lesson, students had exposure to conducting a simple investigation. Now the students will take this investigation one step further by comparing the speeds of several vehicles.


10 minutes

This lesson is the second lesson in a series of lessons on speed.  The previous lesson Which One Is Faster, has the students comparing two different toy cars to see which one is faster.  In this lesson, the students will be ordering a series of four cars from slowest to fastest.  To start the lesson, we begin with a conversation about the previous lesson.

Boys and girls, during our science lesson yesterday, we conducted an investigation to see which car was the fastest.  I want you to think about that investigation.  It was pretty easy because there were just two cars.  What if I had four cars and I wanted to figure out which car was the fastest?  How could I do that if I only had room to test two cars at a time?  I want you to go back to your table group and discuss how that could be done.

I give the students time to converse at their tables to see if they can come up with an investigation that would allow them to figure out which car is the fastest.  I stop at each table and help guide their discussion (see video).  We come back together as a class and the students share their ideas for how the investigation could be conducted.  If the student are not on the right track, I help to steer their ideas in the proper direction to get them to come up with testing pairs of cars and then testing the winners of the pairs against each other and of course, the losers of the pairs so the cars can be ordered from slowest to fastest. 

We then move into the investigation portion of the lesson. 


20 minutes

For this part of the lesson, you will need four "Matchbox" type cars for each group of students.  Label one car of each set "A", "B", "C" and "D" using masking tape.  See sample sample of cars.  You will also need something that can be used as a track for comparing the speeds of 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.

You will also want copies of the simple Investigation Recording Sheet-Four Cars 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 it.

I say to the students, we are going to find out which car is the fastest of the four cars your group has.  To 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 and so on.

We then discuss how we will make sure that the variables (car release, track angle and surface) are controlled during our experiment.  We talk about how the cars cannot be pushed down the track.  I remind them how to use a pencil to hold the cars in place (see photo) and then lift the pencil to start the cars down the track.  We also talk about how we should probably try racing the cars more than once to make sure our results are accurate.

The students conduct the experiment (see video) and record their results when they are done.  The students place the cars in the spaces on the Investigation Grid Sheet (included as a PDF) in order of speed.  We then clean up and gather together for discussion.


10 minutes

To wrap up the investigation, I bring the students back together.  I ask them some questions that I want them to ponder for future investigations that will occur in this unit. 

Was your prediction correct?  Were you able to predict which car was the fastest?

Was there anything you noticed about the cars that were faster than the ones that were slower?  Were they bigger, smaller, heavier, or lighter?

I want you to think...do you think how heavy something is makes a difference in how fast it moves?   Do you think a car that is heavier would be fast or slow?

Tomorrow, we are going to explore this idea a little bit further, so I want you to think about that question some more!