EM120 – Statics
Document1
Example Problem:
Determine the magnitude of the resultant force FR = F1 + F2 and its
direction, measured counterclockwise from the positive x axis.
Assignment:
Describe the steps followed in order to setup and solve this particular
problem.
Student Response (Example 1):
The objective of the problem was to find the magnitude of the resultant force vector, Fr, and its
direction.
The first step is to add vectors F1 and F2 by putting the tail of F2 to the tip of F1 and then connecting the
tip of F2 to the tail of F1 with a line thus creating a triangle. This new line is the resultant vector, Fr. The
angle opposite vector Fr is found by adding the complementary angles of F1 and F2. Use the law of
cosines to find the magnitude of Fr.
The sine of the angle opposite vector Fr divided by the magnitude of Fr is equal to the sine of the angle
opposite vector F2 divided by the magnitude of F2. Solve for the angle opposite F2. To find the direction
of Fr relative to the x-axis, subtract the angle opposite F2 from the angle F1 makes with the x-axis.
Page 1
EM120 – Statics
Document1
Example Problem:
Determine the magnitude of the resultant force FR = F1 + F2 and its
direction, measured counterclockwise from the positive x axis.
Assignment:
Describe the steps followed in order to setup and solve this particular
problem.
Student Response (Example 2):
The objective is to determine the magnitude of the resultant force FR = F1 + F2 and its direction,
measured counterclockwise from the positive x-axis. First we multiply the forces by the cosine
of the angles to find the x component. Then we multiply the forces by the sines of the angles to
find the y component.
We then square the x and y components and add them. Then I take the square root of the sum
to find the magnitude of the resultant force. I then use the law of sines to find the angle of the
resultant force. To do this I take the sine of 90 over the magnitude of FR and multiply it by the y
component. I then take the arcsine of the result, subtract it from the degrees in a circle and this
gives me the angle of the resultant force.
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EM120 – Statics
Document1
Scoring Rubric (Example 1):
Criteria
Has the student provided
sufficient detail that
another beginning Statics
student could reproduce
the approach to the
solution?
Has the student
demonstrated an
understanding of what is
being done in the solution
process?
Is the description written
such that an expert can
understand what the
student means?
Is the description focused
on the approach to the
solution of this problem,
not the specific numbers
of the solution?
Is the assignment
formatted according to
guidelines given?
Full Credit (2 pts.)
Partial Credit (1 pt.)
No Credit (0 pts.)
Identify sequence by
which unknowns are
being found.
One necessary step is
missing or steps are
slightly out of order.
More than one necessary
step is missing or greatly
unordered.
Variables used in each
equation are identified.
Variables used are not
identified in one equation.
Variables used are not
identified for multiple
equations.
Body or particle chosen
for FBD is identified (if
applicable).
Body or particle for FBD
not clearly identified.
Approach described is
fundamentally sound.
One error in the approach
or distracting extraneous
information.
Multiple errors in
approach.
Each equation used is
described in words, not
with algebra.
One equation described
algebraically.
Multiple equations
described algebraically.
Description begins with
the objective(s) of the
problem.
Description does not
begin with the objective
of the problem.
Pronouns have clear
meanings (each sentence
is easily understandable).
One or two sentences are
not clear.
More than two sentences
are not clear.
No problem-specific
quantities are used in the
description.
One problem-specific
quantity is provided in the
description.
More than one problemspecific quantities are
provided in the
description.
Details are provided about
solving this particular
problem.
Description is about how
to solve this type of
problem in general.
Description no longer
than ¾ page typed using
font size and paragraph
spacing indicated.
Description more than ¾
page, but less than 1
page.
Description more than
one full page typed.
Vectors are boldfaced,
scalars are italicized.
One or two
vectors/scalars are not
properly formatted.
More than two
vectors/scalars not
properly formatted.
No figures are present.
One or more figures are
present.
Page 3
EM120 – Statics
Document1
Scoring Rubric (Example 2):
Criteria
Has the student provided
sufficient detail that
another beginning Statics
student could reproduce
the approach to the
solution?
Has the student
demonstrated an
understanding of what is
being done in the solution
process?
Is the description written
such that an expert can
understand what the
student means?
Is the description focused
on the approach to the
solution of this problem,
not the specific numbers
of the solution?
Is the assignment
formatted according to
guidelines given?
Full Credit (2 pts.)
Partial Credit (1 pt.)
No Credit (0 pts.)
Identify sequence by
which unknowns are
being found.
One necessary step is
missing or steps are
slightly out of order.
More than one necessary
step is missing or greatly
unordered.
Variables used in each
equation are identified.
Variables used are not
identified in one equation.
Variables used are not
identified for multiple
equations.
Body or particle chosen
for FBD is identified (if
applicable).
Body or particle for FBD
not clearly identified.
Approach described is
fundamentally sound.
One error in the approach
or distracting extraneous
information.
Multiple errors in
approach.
Each equation used is
described in words, not
with algebra.
One equation described
algebraically.
Multiple equations
described algebraically.
Description begins with
the objective(s) of the
problem.
Description does not
begin with the objective
of the problem.
Pronouns have clear
meanings (each sentence
is easily understandable).
One or two sentences are
not clear.
More than two sentences
are not clear.
No problem-specific
quantities are used in the
description.
One problem-specific
quantity is provided in the
description.
More than one problemspecific quantities are
provided in the
description.
Details are provided about
solving this particular
problem.
Description is about how
to solve this type of
problem in general.
Description no longer
than ¾ page typed using
font size and paragraph
spacing indicated.
Description more than ¾
page, but less than 1
page.
Description more than
one full page typed.
Vectors are boldfaced,
scalars are italicized.
One or two
vectors/scalars are not
properly formatted.
More than two
vectors/scalars not
properly formatted.
No figures are present.
One or more figures are
present.
Page 4