Exploratories

Driving Physics

Problem:

Does a cars odometer measure distance or displacement along the path?

Materials:

An automobile driven according to the rules of the road preferably by an adult

2 additional seat belted passengers for data collection

stopwatch.

Procedure:

1. Drive for at least 10 minutes including stops.

2. In a data table record the trip odometer every 30 seconds, that is, at 0 s, 30 s, 60 s, etc.

3. In the data table record the speedometer reading at 30 second intervals beginning at 15 s, 45 s, 75 s, etc.

 Time (s) Trip Odometer Reading (mi) Speedometer Reading (mph) 0 0 ///////////////////////// 15 //////////////////////// 30 ///////////////////////// 45 ////////////////////////

4. Draw a map of the entire trip. The map will surely involve curves and turns.

5. Plot a displacement-time graph, taking into account any back tracking along the path.

6. Plot a distance-time graph, taking into account any back tracking along the path.

7. On the distance-time and displacement-time graphs the speedometer readings at the appropriate times in a different color.

8. Calculate the average velocity (along the path) for the trip.

Summing Up:

1. Where was the displacement greatest during a 30 second interval? Where on the map did this take place?

2. Where on the map was the car at rest? How was that represented?

3. To what do the negative displacements on the graphs correspond?

4. How did their instantaneous speedometer readings correspond to the shape of the position (displacement)-time graph?