HPP A5
Modeling Human Walking:
Measuring Acceleration
In this investigation we will learn how to actually the calculate acceleration of a person travelling
down a ramp from data on velocity.
GE 1. Velocity and Acceleration of a Person That Is Speeding Up
1. Load the data for the person-cart system accelerated down the ramp with
the smaller height. Start DataStudio if necessary, select File, select Open
Activity, select the file SPEEDUP.ds. Display only Run 1.
Display velocity and acceleration, and adjust the axes if necessary.
2. Calculate the average acceleration of the cart from your acceleration graph.
Select the Smart Tool from the graph menu bar.
Read a number of values (at least five) of the acceleration, which are equally
spaced in time. (Only use values from the portion of the graph after the cart
was released and before the hanging mass reached the floor.)
Calculate the average value of the acceleration.
Accelerations from graph (m/s2):
Acceleration (m/s2)
Statistical average (or mean) acceleration: ________ (m/s2)
Statistical uncertainty in the mean: ________ (m/s2)
Note that you have calculated a statistical average of a sample of acceleration
measurements.
Physicists define average acceleration during a particular time period as the
change in velocity divided by the change in time. We will call this the
“physics” average acceleration to distinguish it from a simple statistical
average. This is the average rate of change of velocity. By definition, the rate
of change of a quantity graphed with respect to time is also the slope of the
Activity Guide
 2010 The Humanized Physics Project
Supported in part by NSF-CCLI Program under grants DUE #00-88712 and DUE #00-88780
HPP A5
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curve. Thus the (average) slope of an object's velocity-time graph is the
(physics) average acceleration of the object.
3. Calculate the average acceleration from your velocity graph. Calculate
the slope of your velocity graph. Read the velocity and time coordinates for
two typical points on the velocity graph. For a more accurate answer, use two
points as far apart in time as possible but still during the time the cart was
speeding up.
Point 1
Velocity _______ m/s
Time ________ sec
Point 2
Velocity _______ m/s
Time ________ sec
Change in velocity:_______ m/s
Time interval:_______
sec
(physics) Average acceleration :_______ m/s2 (Speeding Up)
Calculate the change in velocity between points 1 and 2. Also calculate the
corresponding change in time (time interval). Divide the change in velocity by
the change in time. This is the (physics) average acceleration. Show your
calculations in the table above.
4. Is the acceleration positive or negative? Is this what you expected?
5. Does the (physics) average acceleration you just calculated agree with the
(statistical) average acceleration you calculated from the acceleration graph?
Do you expect them to agree? How would you account for any differences?
GE 2. Speeding Up More
1. Display the data for the person-cart accelerated down the ramp with the
larger height.
Display velocity and acceleration for Run 2 in SPEEDUP.ds.
2. Calculate the average acceleration of the cart from your acceleration graph.
Use the Smart Tool to read acceleration values.
Calculate the average value of the acceleration.
Acceleration (m/s2)
Activity Guide
 2010 The Humanized Physics Project
HPP A5
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Statistical average (or mean) acceleration: ________ (m/s2)
3. Calculate the average acceleration from your velocity graph. Calculate
the slope of your velocity graph. Read the velocity and time coordinates for
two typical points. Remember to use two points as far apart in time as
possible.
Point 1
Velocity _______ m/s
Time ________ sec
Point 2
Velocity _______ m/s
Time ________ sec
Change in velocity:_______ m/s
Time interval:_______
sec
(physics) Average acceleration :_______ m/s2 (Speeding Up 2)
4. Does the average acceleration calculated from velocities and times agree
with the average acceleration you calculated from the acceleration graph?
How would you account for any differences?
5. Compare this average acceleration to that with the smaller ramp height.
Which is larger? Is this what you expected?
Activity Guide
 2010 The Humanized Physics Project