Dedra Demaree
ORAAPT, Oct 2010
Goal-based reform:
Representing
information, conducting
experiments, thinking
divergently, collecting
and analyzing data,
constructing, modifying
and applying
relationships and
explanations, being able
to coordinate these
abilities
 Observe:
• Watch a magnet move within a coil
• ASK students what else they’d like to see
 Model:
• Students brainstorm a quasi-mathematical
statement for induced current BASED ON THE
OBSERVATIONS
 Test:
• Try with different coils, alignments…
 Refine
model then apply: problem
solving, generators…
1.
Understand the problem and devise a plan
a. Read and translate the problem statement.
b. Determine applicable concepts/laws and
assumptions/simplifications.
2.
Represent the problem physically and
mathematically
a. Represent physically.
b. Represent the concepts/laws mathematically.
3.
Carry out the solution
a. Work through the mathematics.
4.
Look back – was your answer as expected,
does it make physical sense?
a. Evaluate the result.
Points:
1 a.
Read and translate
the problem
statement
0
1
No problem
A clear re-statement of
statement is written the problem is given
2
3
1 b.
Determine
applicable
concepts/laws and
assumptions/
simplifications
No information is
given about
assumptions,
concepts or laws
that apply
Trivial or incorrect
assumptions are listed or
only the concepts/laws
are listed
Correct assumptions are given
with no information about
how they relate to the
concepts/laws that will be
used, or an important
assumption is missing
Correct assumptions are listed
along with information about how
they relate to the concepts/laws
that will be used to solve the
problem
2 a.
Represent
physically
No physical
representation is
given
An incorrect physical
representation is given, or
one that is correct, but
does not include any
labels or defined
quantities
A reasonable physical
representation is given, but is
not clearly labeled, does not
define all quantities, or a clear
representation is given but it
contains a mistake
A clearly labeled, correct physical
representation is given, with all
quantities and symbols clearly
defined
2 b. Represent the
concepts/laws
mathematically
No mathematical
representation is
given
A mathematical
representation is given
3 a.
Work through the
mathematics
No solution is
given
Only a partial solution or
an incorrect solution is
given
There is some small mistake
A complete solution with clear
in the solution, or units are
mathematical steps is given, and
neglected, or the mathematical the answer has correct units
steps are unclear
4 a.
Evaluate the result
No evaluation is
given
Very little information is
given to evaluate the
result
A partial explanation is given
for why the result makes sense
(or does not make sense if the
incorrect answer was reached),
and what it tells us about the
physics of the situation
A clear and complete explanation
is given for why the result makes
sense (or does not make sense if
the incorrect answer was
reached), and what it tells us
about the physics of the situation
Read the problem carefully. What are the key words? What
information is given and what will you need to find?
Visualize the situation for yourself, what physically might
happen? Explicitly state what the problem is asking including
clarifying the problem statement. For example, if the problem
states when will the two cars collide, you can state when will
the two cars have the same coordinates for x and t.
Points:
0
1 a.
No problem
Read and statement is
translate
written
the problem
statement
1
A clear restatement of
the problem is
given
2
3
Think what physics concepts/laws are involved and what assumptions you
can make about the physical situation in order to apply those concepts/laws.
What assumptions are reasonable: can you ignore the size of the objects and
consider them particles? Can you ignore friction? In your homework you must
explicitly state how the assumptions simplify the problem and are consistent
with what concepts apply– for example if you are using momentum conservation
for the system of two cars in a collision it means you will be ignoring friction
from the road since that is an external force and you have simplified the system
to no external forces in order to apply a conservation law.
Points
1 b.
Determine
applicable
concepts/laws
and
assumptions/
simplification
s
0
No
information
is given
about
assumptions,
concepts or
laws that
apply
1
Trivial or
incorrect
assumptions are
listed or only the
concepts/laws are
listed
2
Correct assumptions
are given with no
information about
how they relate to
the concepts/laws
that will be used, or
an important
assumption is
missing
3
Correct assumptions
are listed along with
information about how
they relate to the
concepts/laws that will
be used to solve the
problem
Translate the text of the problem into an appropriate type of physical
representation (this may be a picture, a free-body diagram, an energy bar chart, a
ray diagram….). Record all given quantities in the diagram and identify symbolically
(define your symbols!) the relevant variables and unknowns. Choose and show the
coordinate axes. For example, a force diagram should have labeled axes, correct
force arrows of representative length and direction with defined labels (i.e. if you
label an arrow Feb, you must state that e is the earth and b is the box, or if you label
and arrow G you must state that it is the force of gravity acting on the box).
2 a.
Represent
physically
No physical An incorrect
representatio physical
n is given
representation is
given, or one
that is correct,
but does not
include any
labels or defined
quantities
A reasonable
physical
representation is
given, but is not
clearly labeled, does
not define all
quantities, or a clear
representation is
given but it contains
a mistake
A clearly labeled,
correct physical
representation is
given, with all
quantities and
symbols clearly
defined
Use the physical representation to construct a mathematical
representation. Make sure that this representation is consistent with
the physical representation (for example, if you define your origin
above the ground, an object on the ground will not have zero
gravitational potential energy). You should have a symbolical
mathematical statement that clearly shows what concept/law you are
starting with to solve the problem. For example a 1-d kinematics
equation could start with xf = xo + vot + (1/2)at2.
2 b. Represent
the
concepts/laws
mathematically
No
mathematical
representation
is given
A mathematical
representation is
given
Use the mathematical relationships from 2b to clearly solve for the
unknown quantity (quantities). Make sure you include enough steps that
someone can follow your work and that you use consistent units. If you
have set up your problem properly, this step should be purely
mathematics. However, you may find yourself stuck and unable to
completely solve the problem. In that case, go back and check all above
steps to make sure you haven’t overlooked some piece of physics
implied by the situation, or some known relationship such as the fact that
the kinetic friction is proportional to the normal force. Keep symbols in
your solution as long as possible, and when appropriate, only put
numbers in at the final step. Make sure you include units in your final
answer.
3 a.
No solution is
Work through given
the
mathematics
Only a partial
solution or an
incorrect solution
is given
There is some small
mistake in the
solution, or units are
neglected, or the
mathematical steps are
unclear
A complete solution with
clear mathematical steps
is given, and the answer
has correct units
Is the final value you found reasonable? Are the units
appropriate? Does the result make sense in limiting cases?
Does the result make physical sense? Include a written
explanation for why your result makes sense and what it tells
you about what happens in the physical situation.
4 a.
No
Very little
Evaluate the evaluation is information is
result
given
given to evaluate
the result
A partial
explanation is given
for why the result
makes sense (or
does not make sense
if the incorrect
answer was
reached), and what
it tells us about the
physics of the
situation
A clear and complete
explanation is given
for why the result
makes sense (or does
not make sense if the
incorrect answer was
reached), and what it
tells us about the
physics of the
situation
 Observation Experiments
• Can students represent their observations
• Do students clearly distinguish observations and
explanations?
• Can they find a model based on observations?
 Testing Experiments
• Can they make a prediction based on the model?
• Can they draw solid conclusions based on
experiment?
 Application Experiments
• Can they apply knowledge to find something new two
different ways – and judge whether the two methods
are in agreement?
Bullets marked, for example, A3 refer to the application experiment
rubric ability 3. Bullets without such designation are given as
additional guidance. All bullets must be addressed in your lab writeup, and a random subset will be graded.
Design at least two independent experiments to determine the
coefficient of static friction between your shoe and the carpet strip
provided. (You can use any of your group’s shoes, and either the front
of the back of the carpet, whichever gives you ‘cleaner’ data)
Equipment: Force probe, ruler, carpet, board.
Include in your report the following:
a. (A1) Identify the problem to be solved.
b. (A2) Design two reliable experiments that solve the problem.
c. Draw a sketch of your experimental designs.
d. Draw a free-body diagram for the shoe. Include an appropriate set of
co-ordinate axes.
e. (A7) Choose a productive mathematical procedure for solving the
problem. Use the free-body diagram to devise the mathematical
procedure to solve the problem for each experimental set-up.
f. (A3) Discuss how you will use the available experiment to make the
measurements.
g. (A8) Identify the assumptions made in using the mathematical
procedure.
h. (A9) Determine specifically the way in which assumptions might affect
the results.
i. What are the possible sources of experimental uncertainty? How could
you minimize them?
Perform the experiments.
j. Record the outcome of your experiments.
k. (A4) Make a judgment about the results of your experiments.
l. (A5) Evaluate your results by comparing the two independent methods.
Use your uncertainty to make and explicit comparison of the two
values you obtained for the coefficient of static friction.
m. What are possible reasons for the difference?
n. Which experiment was more accurate and why?
o. (A6) Identify the shortcomings in the experiments and suggest
specific improvements.

(55 points) (THIS IS TWO PROBLEMS COMBINED SINCE THEY ARE
ABOUT THE SAME SITUATION) A tall person pushes moves a box up a
10 m long ramp that makes an angle of 10 degrees with respect to the
horizontal, by pushing on it with a push force of 70 N at an angle of 20
degrees below the horizontal (he’s pushing somewhat downward on the
box). The box has a mass of 30 kg, and there is (lucky for you) NO
friction between the box and the floor.
• (10 points) Draw a physical representation for the box for use with Newton’s
•
•
•
•
laws (for part b), making sure to clearly label and define all quantities.
(15 points) If the box starts from rest, find the speed of the box when it
reaches the top of the ramp using Newton’s laws and kinematics. (You must
have an initial equation(s) without numbers in it as a starting point for full
credit.)
(8 points) Draw a physical representation for the box for use with work and
energy (for part d), making sure to clearly label and define all quantities.
(16 points) If the box starts from rest, find the speed of the box when it
reaches the top of the ramp using work and energy. (You must have an initial
equation(s) without numbers in it as a starting point for full credit.)
(6 points) State the assumptions you used FOR PART D and how they
determined what concepts applied.