Student Learning in Motion
Detector- and Video-based
Collision Laboratories
Elizabeth A. George
Maan Jiang Broadstock
Physics Department, Wittenberg
University
Jesús Vázquez-Abad
Département de didactique, Université de
Montréal
Acknowledgements:
Julia Kregenow, Leslie Novak, Theresa Conway, Craig
Hawkins, Ankur Mehrotra (Wittenberg); Nancy
Brousseau, Steve Masson (UdeM)
Supported in part by NSF grant #REC-9804922
Project goal
Study undergraduate students’learning in
laboratories that make use of
microcomputer-based lab (MBL) and
digital video capture and analysis (VBL)
tools
Focus: conservation of momentum and
energy in collisions
Previous research
Student perspective:
•cause and effect (transmission from one
body to another)
•time development (need to analyze what
happens during collision)
N. Grimellini-Tomasini et al., Science Education 77(2),
169-189 (1993)
Capabilities of MBL, VBL tools
•graphs of time dependence of quantities
MBL: real-time
VBL: delayed but replayable
•possible to explore a variety of situations
with relatively quick feedback
Laboratory setup
motion detector
reflectors
motion detector
spring
Used with motion detectors or digital video
capture
produce graphs of x(t), v(t), p(t), KE(t) for
individual gliders
and p(t), KE(t) for system (2 gliders)
Collisions between gliders, between
gliders and spring (“Ballistic pendulum”)
Student-generated data: MBL
Student-generated data: VBL
Momentum vs. Time
0.5
P1
1
P2
1.5
Time (s)
Total KE
2
2.5
Kinetic Energy (J)
Momentum (kg.m/s)
Total P
0.25
0.2
0.15
0.1
0.05
0
-0.05 0
-0.1
-0.15
-0.2
Kinetic Energy vs. Time
KE1
KE2
0.04
0.03
0.02
0.01
0
-0.01 0
0.5
1
1.5
Time (s)
2
2.5
Implementation in introductory
course
Mechanics and Waves, fall 1999,
Wittenberg U.
38 students (37 science majors)
•Several early labs with MBL, VBL, and
photogates
•Collisions (week 10)
•8 MBL
•8 VBL
•22 photogate
•“Ballistic pendulum”(week 11)
•8 MBL
•8 VBL
Sources of data
Observation in lab (videotape)
(MBL, VBL, some photogate)
Lab reports
(all groups)
Individual interviews
(MBL & VBL, between weeks 10 & 11)
Summary questions
(MBL & VBL, week 11)
Written questionnaire (interview +
summary questions) (photogate, week
11)
Summary questions
1. An arrow is travelling at constant
velocity toward a block of hay attached to
a spring which has its other end attached
to a wall. The arrow sticks in the block of
hay and they recoil compressing the
spring.
Compare the momentum and the
mechanical energy for the system
arrow+block+spring at these moments: (1)
just before the arrow hits the hay, (2) just
after the arrow sticks in the hay, (3) when
the spring is compressed to its maximum
amount.
Summary questions
2. Two gliders with bumpers undergo an
elastic collision on an air track. The
following is a graph of their individual (red
and blue) and combined (green) kinetic
energies. Why does the total kinetic
energy drop during the collision and come
back up?
Findings
Students using MBL, VBL tools for the
collision and “ballistic pendulum”labs
•are more likely to draw correct
conclusions from their data
•can easily investigate time development,
what happens during collision; develop
idea of momentum transfer
•exhibit better graph interpretation skills
•perform better on summary questions
Findings
Use of tools, attitudes:
•More between-student discussion with
MBL
•Simultaneous viewing of video + graph
not used
(but students view video during analysis)
•MBL can do more experiments in same
time than VBL
•VBL more enthusiastic, but frustrated by
software problems and data quality
Conceptual difficulties:
•Conservation of momentum overapplied
•p, KE same for objects moving together
(all groups)
•Lack of understanding of “system”(all
groups)
Future Plans
Fall 2000:
modified lab protocols
smoothing of VBL data
availability of MBL, VBL equipment for
entire class
Interviews to focus on some of these
issues