Research%20in%20the%20Teaching%20and%20Learning%20of%20Physics

1
Research in the Teaching and Learning of Physics

• Part II Physics Education Research

2

• Prof. Ss Pretest Posttest ltGgt
• A 97 51 64.5 0.28
• B 192 51 64.3 0.27
• C 70 50 63.6 0.27
• D 119 53 63.6 0.23
• E (n.c) 82 37 53 0.15
• F (hs.h) 24 30 52 0.31
• G (hs.g) 25 30 44 0.20

(Halloun and Hestenes, 1985)
3

• A series circuit consists of three identical
  light bulbs connected
• to a battery as shown here. When the switch S is
  closed, do the
• following increase, decrease, or stay the same?
• The intensities of bulbs A and B
• The intensity of bulb C
• The current drawn from the battery
• The voltage drop across each bulb
• The power dissipated in the circuit

4
For the circuit shown, calculate (a) the current
in the 2 W resistor and (b) the potential
difference between points P and Q.
5

• Find the direction of the acceleration of the
  pendulum bob at each position.

6
Why so bad?

• Constructivismstudents build their own knowledge
• Students not blank slates
• Lectures filtered by initial conceptions
• Unreliability of memory
• Lectures
• Passive learning (no deep processing)

7
Conceptual change theory

• Disequilibrium
• Exploration of alternatives
• Choice of alternative
• Bottom line
• Deep processing
• Formation of links

8
Applications of the theory

• Physics by Inquiry
• Students perform experiments and discuss results
  with peers to develop their own theories
• Workshop Physics
• Students perform experiments and discuss
  consistency with different theories
• Interactive Lecture Demos
• Designed for deep processing of demonstrations
• Peer Instruction

9
Six thousand students
10
Problem Solving

• Expert-novice studies
• Knowledge organization
• Strategies

11
Knowledge organization

• A comparison of novice and expert behavior on
  tasks involving introductory physics problems
  (Chi 1981)
• Study 1 Sort 24 problems into categories
• Novices grouped problems (1, 4), (2, 7)
• Categories Inclined planes, springs, pulleys
• Experts grouped problems (6, 2), (3, 5, 8)
• Categories Energy principles, Momentum
  principles, Newtons Second law

12
Knowledge organization

• Study 2 Repeat with specially designed problems
• e.g., problem 3a vs. changing last sentence to
  With what speed does the man hit the ground?
• categorizations the same for novices and experts

13
Knowledge organization

• Study 3 Say as much as possible about the
  problems in a given category (e.g., inclined
  plane or energy principles) and how they might be
  solved
• Novices talked about surface features of the
  problem angle of incline, length, friction/no
  friction, block, mass of block, forces on block,
  pulley, normal force
• Experts talked about possible solution paths,
  such as conservation of energy or Newtons laws
  and their applicability conditions first before
  describing other factors like the ones mentioned
  by novices

14
Knowledge organization

• Study 4 Give a basic approach for solving a
  problem
• Experts immediately descibed the physics
  principles relevant to solving the problem
• Novices either made very general statements about
  how to proceed (First figure out what is going
  on, then see how different things are related to
  each other), or described the equations they
  would use in solving the problem.

15
Knowledge organization

• Timing information from novice and expert
  attempts to solve a problem (Larkin 1979)
• Bursts versus random separation (chunks)

16
Problem-solving procedures

• Analyzing protocols of solutions
• Experts
• Qualitative analysis
• Multiple representations
• Self-monitoring
• Novices
• Single representations

17
Problem-solving procedures

• Give experts a problem.
• Ignore air resistance. A rigid wheel spins with
  angular velocity w0 about a frictionless axis.
  The wheel drops on a horizontal floor, slips for
  some time, and then rolls without slipping. After
  the wheel starts rolling without slipping, the
  center of mass speed if vf. How does vf depend on
  the kinetic coefficient of friction m between the
  floor and the wheel?

18
Problem-solving procedures

• Similarities between experts and novices
• Had trouble planning a solution
• Had difficulty thinking about both effects
  (friction and slipping time)
• Differences
• Experts visualized the problem and considered
  applicable basic physics principles first
• Experts considered analogies and limiting cases
• Novices confused slipping/rolling cases
• Novices confused linear/angular and
  horizontal/vertical velocities (failed to
  visualize)

19
Curricular implications

• Knowledge organization
• Use of HAT (Mestre, 1993)
• Explicit teaching of structure (Reif and Eylon,
  1984)
• Strategies
• Explicit teaching of strategies and use of
  computers (Heller, 1992 Reif and Allen, 1992)
• Use of different problems (vs. exercises) to
  force more expert-like problem analyses

20
Standard problem
A block with a mass of 5 kg is given a shove and
travels 4 m up a ramp that makes an angle of 20
with the horizontal. If the kinetic coefficient
of friction between the block and the ramp is
0.6, what was the initial speed of the block?
21
Context-rich problem
While visiting a friend in San Francisco you
decide to drive around the city. You turn a
corner and are driving up a steep hill. Suddenly,
a small boy runs out on the street chasing a
ball. You slam on the brakes and skid to a stop
leaving a 50 foot long skid mark on the street.
The boy calmly walks away but a policeman
watching from the sidewalk walks over and gives
you a ticket for speeding. You are still shaking
from the experience when he points out that the
speed limit on this street is 25 mph. After you
recover your wits, you examine the situation more
closely. You determine that the street makes an
angle of 20 with the horizontal and that the
coefficient of static friction between your tires
and the street is 0.80. You also find that the
coefficient of kinetic friction between your
tires and the street is 0.60. Your car's
information book tells you that the mass of your
car is 1570 kg. You weigh 130 lbs. Witnesses say
that the boy had a weight of about 60 lbs and
took 3.0 seconds to cross the 15 foot wide
street. Will you fight the ticket in court?
22
You have an internship in an exobiology
laboratory investigating the possible types of
life that might occur on other planets. Your team
is testing possible mechanisms that a swimming
organism might use to stabilize its temperature.
One of your team suggests that this hypothetical
animal could remove excess heat generated by its
metabolic processes by using a sac of gas similar
to a fishs swim bladder. The sac would be within
the body of the animal near the surface of its
skin. The process would work as follows
First the sac would be isolated from the outside
and gas inside the sac would be in thermal
contact with many small blood vessels in the sac
wall. The sac would slowly expand to its maximum
volume but be kept at constant pressure by
muscles around the sac. While the volume was held
at its maximum, the pressure of the gas would
rise until a maximum pressure was sensed by the
muscles. At that time, blood would be cut off
from the vessels and gill like slits would open
in the animals skin bringing the sac into
thermal contact with the outside fluid that it is
swimming in. The muscles around the sac would
then cause the sac to contract to its minimum
volume while keeping the pressure of the gas
inside constant. Finally, when the sac reached
its minimum size, the muscles would allow the gas
pressure to drop while not changing the volume of
the sac. Then the slits would close, isolating
the sac from the outside fluid and the process
would repeat. Throughout this process no
gas would enter or leave the sac. To determine if
this animal could survive, you decide to
calculate the ratio of the heat output by this
process to the work input necessary to manipulate
the sac. To get some reasonable numbers, you
assume that both the volume of the sac and the
pressure of the gas in the sac double during the
process. You also assume an ideal gas with a
molar specific heat of (3/2)R.
23
Experiment problems
Magnetic Field Measured by U-Loop with
Current An inventor claims that he can
lift objects using a magnetic field and the
current through a wire. You have a model of her
apparatus at your lab table. A U-shaped loop
hangs down from a horizontal support. The bottom
of the loop is between a U-shaped magnet. You are
to evaluate this device for the company for which
you work to see if it has any promise. Run some
current through the loop and note the behavior of
the loop. (a) As a starter, based on your
observations, other measurements with the
apparatus, and the concepts of physics, estimate
the strength of the magnetic field in the region
of the bottom of the U loop. (b) Having learned
more about how the device operates, indicate any
deficiencies that may limit the ability of this
device to be used to lift objects.
24
Jeopardy problems
Q (8.0 mol) (8.31 J/mol K) (361 K) ln(34.3 L/60
L)
F
y
push
F
N
f
26.5
x
W
25
Ranking tasks
Rank these situations from greatest to smallest
on the basis of the pressure on the cork by the
water.
26
Computer coaches

• One obstacle to students acquisition of
  effective problem-solving skills is the
  difficulty in providing them with sufficient
  individualized coaching.
• Computers may be a practical means of providing
  individualized coaching.
• Role of coach is to provide students with
  guidance and feedback while they practice making
  decisions based on effective strategies for
  solving problems.

27
Effective strategies

• Polya (1945)
• Heller and Reif (1984)
• Heller, Keith Anderson (1992)
• Van Heuvelen (1991)

28
Needed cognitive functions

• Students usually focused on implementing
• Inadequate decision-making
• recall of incorrect information
• failure to recall useful information
• non-proceeding procedures
• Inadequate assessment
• incorrect implementations
• failure to learn from mistakes

Deciding Implementing Assessing
Heller and Reif (1984) Reif and Larkin
(1991) Reif and Scott (1999)
29
Computer coaches

• Collection of computer programs, each assisting
  students in solving a single physics problem.
• Problems use kinematics, Newtons laws,
  conservation of energy
• Context-rich problems Heller and Hollabaugh (1992)

30
Reciprocal teaching

• Features
• Student is always actively engaged
• Cognitive functions are practiced in a relevant
  context
• Cognitive functions are modeled by tutor and
  performed by student
• Cognitive demands are higher in second mode

Palincsar Brown (1984)
31
PAL coaches student
3
2
6
4
1
5
32
Student coaches PAL
2
3
1
4
33
Student performs independently
34
Assessment

• Recruited a small number (20) of volunteers to
  test usability
• Students uniformly enthusiastic about being
  coached (interaction mode 1)
• Students not as enthusiastic about coaching PAL
  (interaction mode 2)
• Students dont feel like theyre solving a
  problem
• This mode is more difficult for students
• Mode of interaction may not be helpful for true
  novices

35
Coordination classes

• Elements of a CC
• Causal net
• Reasoning pathways for making inferences
• Readout strategies
• Filters that direct attention to meaningful
  elements
• Performance criteria
• Integration
• Coordination within a single situation
• Invariance
• Coordination between multiple situations

36
Ball on V-track demo
37
Results
Anim 1 Anim 2 Anim 3 Anim 4 Anim 5
one-ball (physics) 8 42 0 0 50
two-ball (physics) 0 17 63 17 4
one-ball (psych) 23 35 0 4 38
two-ball (psych) 15 42 0 8 35
38
Causal nets
Expectations Description and comments
DECEL-UP Speed decreases when rolling uphill (very common)
ACCEL-DOWN Speed increases when rolling downhill (very common)
SAME-SPEED Ball B has same velocity before and after valley (physics-cons. of energy, psych-rare)
NO-GAIN Speed does not increase without cause (ANIM 3)
TIE Balls reach end of track at same time (physics-cons. of energy, speed, psych-low confidence)
39
Read-out strategies
Expectations Fixed-referent Relative-motion
DECEL-UP good sensitivity good sensitivity
ACCEL-DOWN poor sensitivity in 5 systematic error in 5
SAME-SPEED poor sensitivity systematic error in 5
NO-GAIN good sensitivity in 3 poor sensitivity in 3
TIE N/A good sensitivity
Speed and position often confused in relative
motion readouts NO-GAIN insensitivity because
no change in relative position?
40
Decision making

• Common successful process Making read out and
  comparing to expectation
• Identifying an animation as realistic despite
  incompatibility with expectation

Process Effect
Incorrect readouts Limit choices
Incorrect readouts Extend choices
Feedback Change expectations to match readouts
Feedback Change readouts to match expectations
41
Decision making

• Incorrect readouts
• ANIM 5 ruled out for violation of DECEL-UP
• ANIM 2 not ruled out despite violation of
  SAME-SPEED
• Feedback
• Psych students expressing TIE eventually dropped
  it in favor of other expectations
• Physics students expressing TIE used rel. motion
  readouts to choose ANIM 3 (consistently failed to
  report NO-GAIN)

42
Integration and invariance

• Physics students lacked invariance in ANIM 3
• Physics students failed to integrate NO-GAIN
  related readout in final decision
• Psych students did not integrate TIE expectation

43
Conclusion and implications

• Coordination classes are adaptable and can be
  modified based on external data, often without a
  persons awareness
• Students cognition in a particular situation may
  depend on different factors than those in a
  seemingly closely related situation
• Instruction should consider whether errors are
  due to incorrect readouts or incorrect causal nets

44
Epistemology and expectations

• Dimensions
• Structure of knowledge (coherence)
• Nature of knowing and learning (absorption vs.
  constructivism)
• Real-life applicability (lab/class vs. real
  world)
• Evolving knowledge (absolutism vs. extreme
  relativism)
• Source of ability to learn (talent vs. effort)
• Diana study
• Pass-fail, understand physics more deeply (Diana)
• Get a good grade

45

• The most serious criticism which can be urged
  against modern laboratory work in Physics is that
  it often degenerates into a servile following of
  directions, and thus loses all save a purely
  manipulative value. Important as is dexterity in
  the handling and adjustment of apparatus, it can
  not be too strongly emphasized that it is grasp
  of principles, not skill in manipulation which
  should be the primary object of General Physics
  courses.
• Robert Millikan (1903) Mechanics Molecular
  Physics and Heat

46
Learning physics is about as difficult for me as
it is for the average high school student.
47
(No Transcript)