Motion
Graphs and Tracks
Motion Detector
Printed Names:
Signatures:
Date:
Lab Section:
Instructor:
GRADE:
PHYSICS DEPARTMENT
JAMES MADISON UNIVERSITY
Spring 2004
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An Overview of the Basics of Motion:
Motion
In order to describe the world around us we need to have a description as to how things move.
The physicist characterizes and explores motion using the following:
 Position
 Velocity
 Acceleration
 Many other related quantities (Force, Momentum, Mass, Energy…)
In order to exist in our world we need to develop, outside of physics, a very complex
understanding of motion. If we can link our previous knowledge of motion with mathematical
descriptions developed by scientists, we can develop a very good scientific understanding of
motion.
Here are some key points you will need to be able to grasp in order to understand the concept of
motion:
 Position
o Described by three components(distance, direction, time) or a magnitude (how
far) and a direction
o Establish an origin, define positive directions(relative)
o We will refer to position as x throughout the lab

Velocity
o Change in position per unit time
x
t
o Average velocity: based on long time intervals (for example: a long road trip)
o Instantaneous velocity based on very small time intervals (for example: a
speedometer)
o Base velocity values using the same origin and positive directions as position.

Acceleration
o Change in velocity per unit time

v
t
Graphing: Plotting and Relating
o There will always be an x and a y axis.
o Points are plotted accordingly.
In order to gain a fuller understanding of motion you will use the following programs:
Computer Package Activity: Graphs and Tracks
Motion Detector Activity: One dimensional motion
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Part I. Graphs and Tracks Program
Purpose:
Materials:
To improve your understanding of motion and methods for graphing
information. This lab will focus on motion, graphs and their relationship.
Graphs and Tracks software.
This exercise should help students improve their understanding of position, velocity and
acceleration. In general these quantities are vectors. Remember vectors have a magnitude and a
direction. During the semester you will cover the properties of vectors and how to handle them.
Consider position. Students know that specifying a point or location requires more than a single
number. For example, giving directions to the campus center involves specifying both how far to
go and which direction to head. Starting with the common sense methods that are used to give
directions one can begin to understand the rules for vector addition. The importance of vectors
will emerge as you begin to tackle problems of motion in three-dimensional space. This part of
the lab restricts our attention to one-dimensional motion. We will therefore not need to worry
about the vector nature of position, velocity and acceleration. However it is important that
students recognize that ideas developed today will need to be extended.
In order to explore these quantities and their relationships we will use a program
called Graphs and Tracks. There are two parts to the program. We will focus on Part I. which
allows user to adjust the initial settings with slide bars and adjust acceleration by changing the
track.
In order to start the Graphs and Tracks program, click on the Graphs and Tracks icon that
is located on the desktop. If the computer is not yet powered on, you should turn it on. If you are
having difficulties starting your computer or running the Graphs and Tracks program, ask your
instructors or another group that has succeeded for help.
As a general rule, it is usually easier to learn how to accomplish something on the
computer through trial and error. If you have the general idea than pick up the mouse and give it
a try. Don’t be afraid of asking questions, especially at the beginning. Students enter the lab
with the full spectrum of experiences ranging from absolutely no previous knowledge of
computers to complete familiarity.
Once the Graphs and Tracks program is running, choose the option of using the program
for the first time. Each student should then work through the tutorial in order to understand how
the program works. After your group has completed the tutorial, select the Options button at the
top left corner of the computer screen. Scroll down and select Free Exploration. After the new
screen appears, you may begin exploring with the program. You may change the velocity on the
initial velocity bar by moving the cursor in the positive or negative direction. The same thing
may be done with position on the initial position bar. You may also change the track that the ball
will roll on by dragging the columns up or down, making them taller or shorter. Click the ROLL
button to watch the ball roll across the track. To see the results of the ball roll, look at the graph
in the top right corner of your computer screen. You may select the Position, Velocity, or
Acceleration button to view the position vs. time, velocity vs. time, and acceleration vs. time
graphs. This will help you understand the relationship between position, velocity, and
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acceleration with respect to time.
You will then need to work through the problems provided below to master your skills in
this program.
1. Look at this sample graph of position vs. time. Examine the data. Use the information
provided in this graph to create a graph on Free Exploration that matches the graph
below. In order to do this you may have to change the initial position, initial velocity, and
the track until your graph matches the graph below. Once you have matched this position
vs. time graph, click on the velocity and the acceleration buttons above the graph and
examine the graph. Redraw the velocity vs. time and acceleration vs. time in the graphs
provided below based on what you see on the computer screen.
2. Set the initial position to 0 and the initial velocity to 0. Set the track as appears below.
What do you think the position vs. time (x vs. t) graph will look like?
Prediction:
What it actually looks like:
3. Set the initial position to ____ and the initial velocity to -40. Make the track as it appears
below.
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What do you think the position vs. time graph will look like?
Prediction:
What it actually looks like:
Here are some sample situations. Plot your best guesses for the following scenarios. Use a
coordinate system with the origin at far left and positive distances increasing to the right.
1. Sketch the distance vs. time graph for each of the following situations:
An object a rest.
An object moving in the negative direction
with a constant speed
An object moving in the positive direction
with a constant speed
An object that is accelerating in the positive
directions, starting from rest.
2. Sketch the velocity vs. time graph for each of the situations described above.
An object a rest.
An object moving in the positive direction
with a constant speed
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An object moving in the negative direction
with a constant speed
An object that is accelerating in the positive
directions, starting from rest.
Once these are completed we will have an interactive game with the class.
Motion Match
One of the most effective methods of describing motion is to plot graphs of position, velocity,
and acceleration with respect to 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 distance to the object; that is, its position. Logger Pro will perform this calculation
for you. It can then use the change in position to calculate the object’s velocity and acceleration.
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.
walk back and forth
in front of
Motion Detector
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OBJECTIVES



Analyze the motion of a student walking across the room.
Predict, sketch, and test distance vs. time kinematics graphs.
Predict, sketch, and test velocity vs. time kinematics graphs.
MATERIALS
Dell computer
Universal Lab Interface
Logger Pro
Vernier Motion Detector
meter stick
PROCEDURE
Part l. Preliminary Experiments
1. Take a Motion Detector and a ring stand from the back of the room and attach them together
near a computer.
2. Connect the Motion Detector to the Data Logger. (Ask for help if this in unclear).
3. Place the Motion Detector so that it points toward an open space at least 4 m long. You will
use meters to measure your track.
4. Using a meter stick and masking tape, measure 4 m across the room, placing tape at 1 m
increments. Make sure this is in the straight path of the Motion Detector.
5.
Prepare the computer for data collection by opening “Exp 01A” from Intro Physics folder
(see icon on the desktop). One graph will appear on the screen. The vertical axis has distance
scaled from 0 to 5 meters. The horizontal axis has time scaled from 0 to 10 seconds.
6. Using Logger Pro, 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 Collect . Hold a notebook in front of you as you walk away from the Motion
Detector. Walk slowly away from the Motion Detector when you hear it begin to click.
Carefully examine the graph to ensure you understand the measurement.
7. Be prepared to explain what the distance vs. time graph will look like if you walk faster.
Check your prediction with the Motion Detector.
Part Il Distance vs. Time Graph Matching
1. Prepare the computer for data collection by opening “Exp 01B”. The distance vs. time
graph shown will appear.
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2. Discuss how you would walk to produce this target graph. Ask yourself some questions:
Where would you start? At what speed would you need to travel to match the graph?
When would you have to be at rest or at a constant velocity? Etc..
3. To test your prediction, choose a starting position and stand at that point. Start data
collection by having a classmate click Collect . When you hear the Motion Detector begin
to click, walk in such a way that the graph of your motion matches the target graph on the
computer screen.
4. If you were not successful, repeat the process until your motion closely matches the graph
on the screen. It is ok if you do not succeed the first time. Have the instructor initial your
graph when you have a close fit.
5. Prepare the computer for data collection by opening “Exp 01C” and repeat Steps 8 – 10,
using a new target graph.
You can also use this program to work with velocity vs. time and acceleration vs. time.
When you are finished:
1. Shut down the program.
2. Remove the masking tape from the floor.
3. Detach the Motion Detector from the Data Logger.
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4. Detach the Motion Detector from the ring stand and place them back where they were
found.
Complete the following problem in order to show your understanding of the Motion Detector
Activity.
You are walking to class at a constant pace when you accidentally drop your book. You stop
and pick it up. You then continue walking and realize you forgot your notebook in your dorm
room. You run back to your dorm room and stop there to pick it up. Then you run as fast as
you can to your class so you will make it there on time. Create a graph that best represents
this situation.
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