The sequence of 16 video frames of the collision shown above is shown in a composite view at the left

The green line through the cross marks pasted onto the left railway car represents the motion of that car in time;
The red line through the cross marks on the right railway car represents the motion of that car in time.

Students can see this sequence one frame at a time on the computer screen (see data analysis).
Students mark the location of the cross on each railway car using the cursor;
The computer then records the coordinates on the screen where the student has clicked the cursor.
The numbers recorded in this way form the data base from which students can instruct the computer to calculate such derived results as velocity, acceleration, momentum, etc.

The sixteen frames shown are, in real time, 1/30 sec apart. (Standard video records 30 frames per second.) The green line in the composite picture at the left shows that the left car is coming in from the left, moves to the right until it collides with the other car (at time = 7/30 sec), then bounces back in the other direction.
The red line shows that the car at the right is at rest until the collision, and then moves away toward the right. In the next page you will see the composite of computer dots, placed on the computer screen by the student, and the graphs of velocity before and after the collision for each car that the computer can be instructed (by the student) to produce.

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