Item Description:
This event asks the students to determine the average speed of a toy car as it travels six different distances set up by the student. Three trials are to be done for each distance. The only requirement is the longest distance must be at least three times longer than the shortest distance.

Question 1 asks the students to explain why their data may be more accurate for long distances or for short distances. The question is attempting to help the students see that in a very short distance the accuracy of their measurements was limited by the short time interval. If they had difficulty starting and stopping the stopwatch over the specified distance they were actually measuring the instantaneous speed rather than the average speed.

A good response will show the student can interpret the results they obtained. The speed of the toy car should have been approximately the same for the three trials at the longer distances than it was at the shorter distances. The precision of their instruments may also have limited their ability to measure the time over a very short distance.

Question 2 asks the students to describe an experiment to determine if cars that pass by the school are speeding. The question is really asking them to apply the concept they learned and used in the experiment, that the average speed of an object is the distance traveled divided by the time it takes to travel this distance.

A good response will show the student can apply this concept to an actual situation. The experiment should include measurement of the distance between two points that the car will pass by and a method to determine the time it takes to travel that distance.

Comment: Many students answered question 2 by stating a policeman should use a radar gun to see which cars are speeding. To eliminate this problem, the question could have begun with "You are given a stop watch and a measuring tape."

Criterion

1		Long distance with or without explanation (Q1) OR short distances with explanation based on experiment (Q1)
2		An experiment is described. (Q2)
3		Experiment includes at least one of these: (Q2) - time, distance, accuracy (repeated observations)
4		Experiment includes time and distance (Q2) and accuracy is understood (Q1 or Q2).

Criterion 1:
It is stated that the data is more accurate for long distances with or without an explanation.

The following do not meet this criterion:
a.  Short because we could time it better.
b.  Short because the car would slow down when it went far.

Criterion 2:
An experiment of some type is described to determine if cars passing the school are speeding. (Q2)   For example:
a.  Use a radar gun from the police.
b.  Drive a car by at 25 mph and see how many cars pass it.

Criterion 3:
The experiment includes at least one of the following: (question 2)
A.  The experiment includes measurement of time.
B.  The experiment includes setting up a distance to observe the cars traveling by the school.
C.  The student recognizes that to achieve more accurate results the experiment should be repeated (more than one car must be observed).

Criterion 4:
Both of the following are met (from criteria 3):
A.  The experiment includes measurement of time (question 2).
B.  The experiment includes setting up a distance to observe the cars traveling by the school (question 2).