Mobile Project – Pre-AP Geometry
You will create a Mobile using the center of mass for different geometric shapes. The main goal is to
learn about centers of mass in a practical way. Therefore, your constructions (blueprint) will be very
important.
You will also want your mobile to look as professional as possible. Your hanging frame will make or
break the look of your mobile. Possible materials for the frame include stiff wire or balsa wood. There are
many examples on the internet that you can use for ideas and inspiration.
You will need something stiff yet attractive for your triangles. You may use stiff cardboard, poster
board or craft wood, or plastic (if you can cut it safely!). You will first trace your shapes on paper, and find
the center of mass (centroid) using a compass and straight edge then transfer the centroid to your shape. You
will need string (no fishing line since it is invisible and impossible to untangle) to hang your triangles from the
frame. Think about how to get your triangles to hang evenly. You may need a bead underneath to keep the
triangles straight. You may NOT screw or glue the string to the triangles!
The mobile itself will be graded on centroid alignment (does it hang parallel to the floor?), visual
appeal and quality of constructions. Your blueprint will be graded on accuracy of constructions and on the
presence of all required elements. The grading rubric is attached. Please turn in the rubric with the mobile
and blueprint.
The project is due on __________________________.
Name _______________________________
Period _________
Mobile Project Rubric
Mobile
Visual
Appeal
Professional
Satisfactory
Unsatisfactory
Poor
3 points
2 points
1 point
0 points
Creative and/or
decorative (with
interesting patterns,
colorful, or coherent
theme)
Some creativity; use
of patterns or colors
but no coherent
theme.
Minimal color or
patterns.
No colors,
patterns or
coherent
theme.
Quality
Sturdy triangles, frame
is steady and hangs
straight, strings aren’t
tangled --looks
professional.
One problem such as:
triangles are not
sturdy OR frame
doesn’t hang
perfectly even.
More than one of the
following: triangles
are not sturdy, frames
don’t hang evenly,
strings are tangled.
Floppy or bent
triangles,
tangled, used a
coat hanger,
appears
“slapped
together.”
Alignment
All triangles hang by
the centroid and are
perfectly level
(horizontal).
Most triangles hang
by the centroid and
are perfectly level.
Less than half of the
triangles hang level.
None of the
triangles are
level.
A “life size”
diagram/blueprint of
each triangle is
included along with
construction* marks
which are correct,
accurate, and clear.
“Life size” Diagrams
accurate and most
construction marks
are shown, but may
be disorganized or
missing some on
some sides OR are a
bit off. There may be
one or two small
mistakes
Disorganized, not
drawn to scale, no
construction marks,
some triangles
missing. There are
three or more
mistakes in the
constructions.
No construction
marks OR most
constructions
are incorrect.
Has 5 of the different
types of triangles. At
least 5 all-together.
Contains 4 different
types of triangles or
less than 5 alltogether.
Contains 3 different
types of triangles or
less than 5 alltogether.
Contains less
than 3 different
types of
triangle, and/or
less than 5 alltogether.
Blueprints
Accuracy
Variety
*Construction marks refer to the bisectors (or midpoint) of the sides and centroid.