1. Inquiring Minds Want to Know:
Was He Speeding?
Momentum, Collisions, and Mathematical Relationships
Kristin Angello
kristin.angello@gmail.com 1

2. Before Collision:
TOWN POLICE
Automobile Collision Report
A Honda Odyssey minivan was
parked legally on the shoulder
of Tulip Road. A Toyota Corolla Tulip Road
was turning onto Tulip Road from
Daisy Drive. The Corolla
Daisy Drive
collided into the van broad side,
resulting in the van travelling
2.3 meters before coming to
rest. After Collision:
No skid marks were observed.
No witnesses, aside from the
driver of the Corolla, were
2.3m
present. No injuries were
reported.
Tulip Road
Daisy Dr. 2

3. Was Speed a Factor in this Crash?
The police need help in developing a method to determine the
speed of the car right before it hit the van.
What do we know about physics that could help the police
determine whether or not the driver was speeding?
 momentum = mass x velocity
 A change in momentum can be related to force
Consider this: What if we simulated
the crash in our lab? What if we
crashed the car into the van at
different velocities? What would that
tell us?
3

4. Goals of Laboratory Exercise
1. Students will develop a
laboratory procedure to
simulate a real-life
situation in the laboratory.
0.07
Relationship Between Velocity of Car and
Distance Van Moved
0.06 2. Students will interpret graphs
to determine the mathematical
Distance Van Moved (m)
0.05
0.04
relationship between two
0.03
variables.
y = 0.0188x + 0.0061
0.02
R² = 0.95822
3. Students will understand that
0.01
the impulse imparted to an
0.00 object causes a change in its
momentum.
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
Velocity of Car (m/s)
4

5. Students’ Thinking (guided by teacher)
The distance the van moves depends on
the velocity of the car.
Let’s crash the car into the van at
different velocities and measure the
distance the van moves.
We’ll use a motion sensor to measure the
velocity of the car.
We can use a centimeter ruler to measure
the distance the van moves.
5

6. Student-Developed Procedure
Computer Motion Detector
(Connected to
Motion Detector)
“minivan” “car”
6

7. Recording Data
Velocity of Car
Distance Van Moved
After Collision
7

8. Minimizing Error, Maximizing Success
Each group will be • Assigning velocities to each group
assigned 2 different will ensure that the class data will
cover a wide range of velocities
velocities
• Students will verify their data with
Each velocity will be another group that took
assigned to 2 groups measurements at the same velocity
Each group will collect • Multiple trials will reduce the
data at least 3 times influence of data anomalies and
error
for each velocity
8

9. Students input their data into a
class spreadsheet
9

10. Students develop a graph and a
“best fit” line, displaying the
equation of the line on the graph
Relationship Between Velocity of Car and Distance Van Moved
7.0
6.0
Distance Van Moved (cm)
5.0
4.0
3.0 Class Data
Linear (Class Data)
2.0
1.0
y = 0.0188x + 0.0061
R² = 0.95822
0.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Velocity of Car (m/s)
10

11. Post-Lab Discussion
 What are your observations about the best fit line? Why do
you think it depicts a linear relationship rather than a
logarithmic or quadratic relationship?
 Using the equation we developed, can you estimate how far
the van would move if the car had a velocity of 1.0m/s?
 Would this equation work for Lego cars of different masses?
Why not? How can we use the class data to develop a chart
for momentum of car vs. distance van moved? How could
that information be useful to crash scene investigators?
 How can what we learned today help the police develop a
method to determine if the driver of the car was speeding?
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12. References
Laboratory exercise adapted from:
Bonneau, Jacklyn. (2007). Forensics with Vernier. Sargent-Welch, New
York.
Images:
Slide 1: http://local.stv.tv/aberdeen/news/24840-man-suffers-minor-injuries-as-
van-collides-with-wall/
Slide 2:http://www.seedsofgrowth.com/the-power-of-realtime-feedback-for-your-
business
Slide 4: http://oregonstate.edu/terra/2008/09/pipeline-to-science/
Slide 9:
http://www.visualphotos.com/image/2x4778942/germany_emmering_students_us
ing_computer_in
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