HPP A12v1
Modeling Your Motion When Jumping
Modeling Your Motion When Jumping
 Review the Hints for Using DataStudio (Reference D) before coming to this lab.
Studying how the motion sensor works
In Lab #02, you were introduced to the motion sensor and used it to study your motion.
How do you think it works? Discuss with your partners what you think it is actually measuring
and how it is able to display graphical models of position, velocity, and acceleration.
1.
Record some brief notes about your discussion and ideas.
Obtain a large ball from the equipment table. Turn on the interface and start up the
computer. Open the file MBL – Overhead Motion Table. This file is set to record data for one
second.
Have one member of your group take the ball and hold it underneath the motion sensor
as data is collected. Hold the ball as still as possible. You might even hold your breath as the
data is collected.
Once you have collected a good set of data, examine the number displays on the
computer. Record 5 consecutive pairs of these numbers in a table in your logbook. Use these
five pairs of time and position data to answer the following questions.
2.
(a)
What is the time interval between each measurement of distance? How do you
know?
(b)
Look at the values of position. Are they all the same or do they vary? What would
you estimate is the uncertainty in a distance measurement by the motion sensor?
(c)
Based on the data table, what procedure(s) do you think the computer could use to
estimate the velocity values? Explain, giving an example of a calculation using the
numbers in the table. Calculate 3 sample velocity values.
(d)
Based on the motion of the ball, what value(s) would you expect for its velocity? Do
your calculations agree? If not, can you explain why they may not be exactly the
same?
 Humanized Physics Project
2005 - UNL
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It turns out that the computer is using the same methods to calculate velocity (x/t
where t is small) and acceleration (v/t where t is small) as you have just done. It just is
able to do it very quickly and it also averages over a few points each time to make the graphical
models more smooth.
 Humanized Physics Project
2005 - UNL
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Modeling Your Motion When Jumping
Now that you understand a little better how the motion sensor works, you are ready to
use it to study more about motion. Today you will be analyzing the motion of your own body
as you jump into the air. However, before you work on such a complicated system, you should
start by analyzing something a little more simple, namely the motion of a ball being tossed
straight up into the air.
You will be collecting 3 sets of data today and, assuming there are three people in your
group, each of you should take a turn being the person to hold the ball, toss the ball, or jump.
Exploring what happens when you toss a ball up into the air and catch it
Quit DataStudio and open the file MBL – Overhead Motion. Pick a person to toss the ball
up into the air. Have this person practice tossing it straight up while the other partner(s)
observe the ball's resulting motion. Try to toss the ball so that it gets no closer than about a foot
in front of the motion sensor.
Data Collection
Now you are ready to collect data. Start by holding the ball low, so that you only move
the object upward, and then toss it vertically upward toward the motion detector mounted on
the overhead support beam and catch it as it falls back down. Record its motion using the MBL
– Overhead Motion file.
Use the software to plot distance, velocity, and acceleration as functions of time. Your
graphs should show the data from before you start to toss it up until after you caught it on the
way back down.
Repeat the procedure until you have collected a "good" set of relatively smooth data.
Adjust the graphs so that they display the data from when the ball was motionless (just before
you started to toss it) until just after you caught it. Do not show a lot of extra data. In addition,
adjust the range of the vertical axes so that the data fills most of the graph.
Once your graphs are adjusted, print copies for each person in your group and affix
them into your logbook. Record the name of the person who did the tossing.
Data Analysis
Use your printed graphs and observations of the ball's motion to answer the following
questions.
 Humanized Physics Project
2005 - UNL
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Modeling Your Motion When Jumping
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2005 - UNL
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Distance vs. Time
3.
(a)
Label the following events on your distance graph: Ball held in hand; Ball just
leaving the hand; Ball at the highest point; and Ball just starting to be caught.
(b)
Look on the graph for times when the distance was positive, was negative, and was
zero, if they occurred. Describe in words how the ball was moving when each of
these occurred. If they did not occur, explain why not.
(c)
How far did the ball travel from when it left the hand to when it reached its highest
point?
(d)
In words describe the shape of the graphical model of the ball's distance vs. time
while it was in the air. What kind of mathematical function model might describe
this shape?
Velocity vs. Time
4.
(a)
Label one example of each of the following events on your velocity graph: Ball at the
highest point; Ball speeding up; and Ball slowing down.
(b)
Look on the graph for times when the velocity was positive, was negative, and was
zero, if they occurred. Describe in words how the ball was moving when these
occurred. If they did not occur, explain why not.
(c)
At what point in the motion did the ball have the fastest speed? The slowest speed?
What were these speeds?
(d)
In words describe the shape of the graphical model of the ball's velocity vs. time
while it was in the air. What kind of mathematical function model might describe
this shape?
Acceleration vs. Time
5.
(a)
Label each of the following events on your acceleration graph: The acceleration
when the ball was in the air; Maximum acceleration magnitude; and Minimum
acceleration magnitude.
(b)
Look on the graph for instances where the acceleration was positive, was negative,
and was zero, if they occurred. Describe in words how the ball was moving when
these occurred. If they did not occur, explain why not.
(c)
What was the maximum magnitude of the acceleration? What was happening to the
ball when this occurred?
(d)
Consider the data for when the ball was in the air. What was the acceleration
(magnitude and direction) of the ball as it traveled up? At the highest point? As it
traveled back down? What is the average of these three values?
 Humanized Physics Project
2005 - UNL
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(e)
In words describe the shape of the graphical model of the ball's acceleration vs. time
while it was in the air. What kind of mathematical function model might describe
this shape?
 Humanized Physics Project
2005 - UNL
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DataStudio Tip:
You can use the software tools to do calculations for you, such as calculating an average
(Mean) or finding a slope (Linear Fit). The procedures for these tools are described below.
Data Statistics:

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Click once on the graph of interest.
Select the kind of statistic (i.e., Mean)
Use the mouse to select the data of interest.
Curve Fitting:
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6.
Click once on the graph of interest.
Select the kind of fit (i.e., Linear).
Use the mouse to select the data of interest.
Using the software tools, determine (a) the slope of the velocity graph and (b) the average
acceleration of the ball when it was in the air. Describe your procedures and record your
results.
(c) How well do these two values compare? (Hint, calculate a percent difference.)
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2005 - UNL
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Invention Discussion
Share your answers to questions 5c (maximum acceleration magnitude) and 6a-b
(average in-flight acceleration) with the class. Your instructor will lead a discussion of
important concepts related to this lesson. Record a summary of this discussion in your logbook.
Application Activity #1: Jumping Up from a Crouched Position
Pick a new person to be the subject for this experiment. Repeat the exploration activity,
only this time don’t throw an object but instead, use your body as the object and jump up off of
the floor. Start from a motionless, crouched position (before you start taking data) and move
your body only upward. Try to keep your arms as still as possible.
Repeat until you have collected a good set of data, always starting from a motionless,
crouched position. This may take a few jumps since the motion sensor may have a hard time
measuring your motion if you move side to side. You may want to jump several times during
one run and then adjust the axes to show only the complete motion of one jump. If you do this,
always start by remaining still (in a crouched position) so you have that reference on your
graphs.
When you have good graphs of your motion, adjust the graphs to best display the data
and print them out for each person. On the printout, label the name of the person who jumped.
7.
Using words, describe in detail the motion of the jumper's body and how this motion is
represented in each of the three graphs. Label all distinguishing features on the graphs
such as when leaving the floor, when hitting the floor, and when closest to the sensor.
8.
Examine what was occurring when the jumper was at the highest point. What were the
values of his/her position, velocity, and acceleration at that time?
9.
Using the same procedure(s) as you used in question 6, determine and record the average
acceleration of the jumper when he/she was in the air. Describe how you determined this
value. How does it compare to your answer to question 6?
10.
(a)
Suppose that time = 0.0 s at the instant the jumper left the floor. Write a functional
model that represents the jumper's velocity vs. time while he/she was in the air.
Explain why you think this model is appropriate.
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2005 - UNL
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(b)
Suppose that time = 0.0 s at the instant the jumper left the floor. Write a functional
model that represents the jumper's acceleration vs. time while he/she was in the air.
Explain why you think this model is appropriate.
 Humanized Physics Project
2005 - UNL
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11.
Modeling Your Motion When Jumping
Last lab, you recorded data as you walked toward the motion sensor and back away from
the sensor. This motion sounds similar to the motion of the jumper who also moved
toward the sensor and then away from the sensor while in the air.
(a)
Make a sketch of the graphical model of the velocity of a person walking forward
and then backward in front of the motion sensor. In addition, make a separate
sketch of the graphical model of the velocity of a person in flight on the way up and
on the way down.
(b)
Compare and contrast the shapes of the velocity graphs for these two motions.
(c)
Which motion is an example of constant, non-zero acceleration and which is an
example of constant, non-zero velocity? Explain.
End of Lab Procedures

Return the ball to the equipment table.

Quit the Data Studio software program by selecting "Quit" under the "File" menu.

If this is the last lab section of the day, then "Shut down" your computer and turn
the power off to the interface box.
Want More Information?
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Position, Distance, and Displacement (see Walker, Section 2-1)
Speed and velocity and their graphical interpretation (see Walker, Sections 2-2 & 2-3)
Acceleration and its graphical interpretation (see Walker, Section 2-4)
Motion with constant acceleration and falling objects (see Walker, Section 2-5 – 2-7)
Using the DataStudio software (see Reference D)
 Humanized Physics Project
2005 - UNL
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