Motion: Speed of Automobiles

This activity will allow students to determine the speed of a moving automobile by use of a stopwatch and a meter stick. They will analyze data and convert measurement from meters/sec into miles/hr. Students will apply skills of observation, field techniques, and equipment operation. After completing this activity students should understand average velocity is the change in position divided by the change in time, and is different than instantaneous velocity. Velocity can be represented graphically and is not the same as speed.

This activity in designed for grades 9-12 general physics course, but could be adapted for a physical science course. This is a one day (50 minute) activity done outside.

Equipment: Per group of 3: stopwatch, meter stick, pencil, & paper

This activity is used as reinforcement to help students better understand the concept of velocity. It would be easy to adapt this activity to any moving objects besides cars (people, bikers, runners, etc).

This activity could begin with a discussion on how we could determine the velocity of a car without looking at the speedometer. The materials needed per group of 3 are a stopwatch, meter stick, pencil, and paper. Each group will measure out 40 meters. Have student A at one end as a starter. When a car goes by, Student A (with arm up) will rapidly lower his/her arm. Student B will be at the other end. When student A's arm goes down, Student B will begin the time. Once the car reaches students B, he/she will stop the stopwatch. Student C will record the time in a chart. Do 4 trials. Calculate the speed for each trial, and convert from m/s to mi/hr. To conclude the activity the class could determine how many people were driving over the speed limit based on the speed limit of the road where data was collected from.

Safety is very important in this lab. It is done outside near the road, so a safe location needs to be picked out prior to the lesson. Once groups of 3 are chosen I would recommend they assign the student A, B, & C roles before going outside. This is my first year teaching physics, so I have never done this activity. I anticipate that the results of the data could also be graphed and discussed as a class.

Students will hand in there data tables from activity day. They will answer these 2 questions:
1. Were there any cars breaking the speed limit law?
2. What were some errors that could cause the answer to be off?

9.2.2.2.2 Explain and calculate the acceleration of an object subjected to a set of forces in one dimension.