HPP A1v1
Modeling Human Walking:
Distance and Time
We want to investigate how humans move around in the world. Certainly an important, every
day, technique used by most people is walking. Let's try to understand this activity in a precise
way.
GE 1.
1. Why might a physical therapist, sports medicine physician, or orthopedic
specialist want to have a description of normal walking behavior? In other
words, why should we bother developing a quantitative description of
walking?
2. Stand up and try to walk. Notice carefully what your body must do to start
this motion. Describe any pushes or pulls (forces) in your body that must
occur to get your body moving.
3. Describe pushes or pulls from outside your body that must occur to get your
body moving.
4. Once you start moving, do all parts of your body move in the same way?
5. Go to the Video folder in the Course Documents area of the course web
page. View the video "Man Walking". If you wanted a fairly complete
description of this motion, how many separate body parts would you have to
follow?
Activity Guide
 2002-2010 The Humanized Physics Project
Supported in part by NSF-CCLI Program under grants DUE #00-88712 and DUE #00-88780
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6. Tape a large DOT on the side of one person's body. Observe the DOT as
the person walks. How is the dot's motion similar to the person's motion?
How is it different?
The systematic study of body motion during movements such as walking and running is called
gait analysis. Pathologies in gait can be indicators of underlying muscle, nerve, and orthopedic
problems, so correct identification of such pathologies can be important in returning people back
to good health. Identifying subtle pathologies involves more than simply making qualitative
visual observations.
Even a simple human motion such as walking is complicated. Physicists often approach a
complex system by focusing on a few aspects of the system. Once we can describe those aspects,
additions can be made. We will do that here, in our study of walking. For the next few
activities, we will treat the body as one object and try to describe the motion. Eventually we will
return to the more complex problem of describing walking and running gaits in a real human
being.
In this investigation, you will use a motion detector to plot a distance (position)-time graph of
your motion. As you walk (or jump, or run), the graph on the computer screen displays how far
away from the detector you are.
• "Distance" is short for "distance from the motion detector."
• The motion detector is the origin from which distances are measured.
• It detects the closest object directly in front of it (including your arms if you swing them as you
walk).
• It will not correctly measure anything closer than 1/2 meter. When making your graphs don't go
closer than 40 [cm] from the motion detector.
GE 2. Making Distance-Time Graphs
1. Open the DataStudio program. To start the program, use the mouse to
click on Start -> Programs -> Physics -> DataStudio. Select File, select Open
Activity then select Distance.ds. The graph axes should appear on the screen.
Activity Guide
 2002-2010 The Humanized Physics Project
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2. When you are ready to start graphing distance, click once on the Start
"button" in the upper menu on the screen.
3. Stand still and collect data first. Measure the distance from the front of the
detector to you. Does the graphed distance agree with this measurement?
How accurate is the motion detector?
4. Make distance-time graphs for different walking speeds and directions
according to the following directions.
5. Select the graph in DataStudio and then Edit>Copy, return to Word and
select the appropriate table cell on the next page, select Edit>Paste Special…,
and from the menu select Bitmap and deselect Float over text.
a. Start 1/2 meter from the motion
detector and make a
distance vs. time graph
by walking away from
the detector (origin)
slowly and steadily.
Paste the graph into the cell on the right.
b. Make a distance vs. time graph by
walking away from the
detector medium fast
and steadily.
Paste the graph into the cell on the right.
c. Make a distance vs. time graph by
walkding toward the
detector slowly and
steadily.
Paste the graph into the cell on the right.
Activity Guide
 2002-2010 The Humanized Physics Project
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d. Make a distance vs. time graph by
walking toward the
detector medium fast
and steadily.
Paste the graph into the cell on the right.
6. Describe the difference(s) between the graph you made by walking away
slowly and the one made by walking away more quickly.
7. Describe the difference(s) between the graph made by walking toward and
the one made walking away from the motion detector.
8. Predict the graph produced when a person starts at the 1-meter mark, walks
away from the detector slowly and steadily for 4 seconds, stops for 4 seconds,
and then walks toward the detector quickly. Compare predictions with the rest
of your group. Draw your group’s prediction on the left axes in the table
below by double clicking on the graph and using the drawing tool (pencil) to
sketch the line. Sketch any dissenting views in your group with a dashed line.
Prediction
Final Result
9. Do the experiment. Move in the way described and graph your motion.
When you are satisfied with your graph, copy the graph from DataStudio and
paste the bitmap into the table cell on the right above.
Activity Guide
 2002-2010 The Humanized Physics Project
HPP A1v1
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10. Is your prediction the same as the final result? If not, describe how you
would move to make a graph that looks like your prediction.
GE3. Matching a Distance Graph
In this activity you will match a distance graph shown on the computer screen.
1. Display the distance graph on the screen. Download the file match_d.ds
from the course web page. Open it in Data Studio. The distance graph below
will appear on the screen.
2. Move your body to match the distance graph shown on the computer
screen. You must move to duplicate the graph. You may try a number of
times. Work as a team. Get the times right. Get the distances right. Each
person must take a turn and paste the graphs below.
What was the difference in the way you moved to produce the two differently
sloped parts of the graph you just matched?
GE 4. Other Distance-Time Graphs
1. Now load the activity match_d2.ds and try to match it.
Each of you must do this! Paste your results here.
Activity Guide
 2002-2010 The Humanized Physics Project
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2. Can you make a curved distance-time graph? Try to make each of the graphs shown below.
D
i
s
t
D
i
s
t
Time
Graph 1
D
i
s
t
Time
Graph 2
Time
Graph 3
Describe how you must move to produce a distance-time graph with each of the shapes shown.
Graph 1 answer:
Graph 2 answer:
Graph 3 answer:
Invention
In the above activities, we have used the word distance to refer to location of an object.
Physicists would prefer to be more precise in their use of language. There are at least three terms
that are of use in discussing the location of an object.
Position: if you construct coordinate axes, such as putting a ruler down on the floor, the number
on the ruler marking your location would be called your position. Often, we indicate position
with the variable x.
Displacement: when you walk you go from one location to another location. If you are walking
along a rule you can indicate a beginning position and an ending position. The change in
position is defined as your displacement.
Distance: a displacement could be a positive number or a negative number. Sometimes we are
only interested in the magnitude of the displacement, and not whether it was positive or negative.
The magnitude of the displacement is called the distance traveled. So, here we are using the
word distance in a slightly more precise way than in common usage.
Activity Guide
 2002-2010 The Humanized Physics Project