Graph Matching
One of the most effective methods of describing motion is to plot graphs of position, velocity,
and acceleration vs. time. From such a graphical representation, it is possible to determine in
what direction an object is going, how fast it is moving, how far it traveled, and whether it is
speeding up or slowing down. In this experiment, you will use a Motion Detector to determine
this information by plotting a real time graph of your motion as you move across the classroom.
The Motion Detector measures the time it takes for a high frequency sound pulse to travel from
the detector to an object and back. Using this round-trip time and the speed of sound, you can
determine the position of the object. The GLX will perform this calculation for you. It can then
use the change in position to calculate the object’s velocity and acceleration. ( Highlight the
variable in the GLX and press the options key.) All of this information can be displayed either
as a table or a graph. A qualitative analysis of the graphs of your motion will help you develop
an understanding of the concepts of kinematics.
OBJECTIVES

Analyze the motion of a student walking across the room.
 Predict, sketch, and test position vs. time kinematics graphs.
 Predict, sketch, and test velocity vs. time kinematics graphs.
MATERIALS - MOTION DETECTOR, GLX, METER STICK, MASKING TAPE
PRELIMINARY QUESTIONS
USING A PIECE OF GRAPH PAPER SUPPLIED BY YOUR INSTRUCTOR..........
1. Use a coordinate system with the origin at far left and positive positions increasing to the
right. Sketch the position vs. time graph for each of the following situations, using a separate
graph for each.

An object at rest
 An object moving in the positive direction with a constant speed
 An object moving in the negative direction with a constant speed
 An object that is accelerating in the positive direction, starting from rest
2. Sketch the velocity vs. time graph for each of the situations described above, using a separate
graph for each.
Physics - Smith
PROCEDURE
Part l Preliminary Experiments
1. Connect the Motion Detector to the GLX.
2. Place the Motion Detector so that it points toward an open space at least 6 m long. Use short
strips of masking tape on the floor to mark the 1 m, 2 m, 3 m, and 4 m positions from the
Motion Detector.
3. Turn on the GLX and a graph of distance vs. time should appear. Chose the sensor option for
people. Using the GLX, produce a graph of your motion when you walk away from the
detector with constant velocity. To do this, stand about 1 m from the Motion Detector and
have your lab partner click the play button. Walk slowly away from the Motion Detector
when you hear it begin to click. You should produce a graph of your motion when you wak
away from the detector at constant velocity.
4. Next, try to make the graph of the sketch you made in the preliminary question 1b (object
moving in the positive direction with constant speed), matching the slope of the line.
5. Save the 2 graphs that you made to a file in the GLX.
Part Il - Graph Matching
1. For each graph listed below, describe how you would walk to produce the target graphs. List this next
to the graphs. Then using your GLX, test your prediction. Repeat the process until you are successful
with each graph. Save each graph data file in the GLX. Remove the duct tape when you are finished.
Your lab group will print off one copy of each of your 6 graphs to be turned in.
Graph Match 1
3.5
3
2.5
2
Distance (meters)
1.5
1
0.5
0
1 2 3 4 5 6 7 8 9 10 11 12 13
x axis is time in seconds for all graphs
Graph Match 2
5
4
3
Distance (meters)
2
1
0
1
2
3
4
5
6
7
8
9 10 11 12 13
Graph Match 3
7
6
5
4
Distance (meters)
3
2
1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14
( Highlight the variable in the GLX and press the options key for the graph in lab 4)
Graph Match 4
2.5
2
1.5
Velocity
(meters/sec)
1
0.5
0
1
2
3
4
5
6
7
8
9
10
Post Lab Questions
1. Explain the significance of the slopes in the graphs of the distance vs. time graphs, including positive
and negative slopes and the steepness of the slope.
2. Explain the difference in the motion for graphs 1 and 2 verses 3 and 4.
3. What made the graphs easier or more difficult to make?
4. What challenges did you overcome?
5. What were your sources of error?
Turn in your initial hand -made graphs that you made as a group, as well as your individual
preliminary graphs.