Anticipatory Set
Have students immediately get situated in project groups.
Entertain questions regarding the grading rubric.
Show two examples of unsuccessful bridges (modeling).
Ask students for their thoughts about the bridges, and
have them predict if they are strong or not, giving
reasons for their hypothesis. Model the weighing
technique and show the weaknesses of the bridges.
Discuss the hypotheses after the weigh-in; were the
hypotheses correct? Why or why not?
Ask students if the simplicity, small number of
angles, weak supports, weak ties, height, shape, or
materials played any role in the strength of the
bridge. Anticipate answers like sloppy construction
and simplicity prevented the bridge from being strong
(suggesting the importance of numerous angles to
distribute the load). Some students may also remark
on the materials; for example, straws weaker than
balsa wood.
Also ask for efficient construction techniques. How
could all of the diagonal pieces be quickly measured
and cut? How could you maintain consist angle
measures for certain parts of the bridge? Hopefully
students will remark on translation, rotation, or
reflection, allowing for a teachable moment to ensure
understanding. If a teachable moment is necessary
because not all students understand these geometric
ideas, sketch the main points and examples on the
board. This will help bridge construction and plant
the seed for future geometry topics.
Day Two: 1
Stated Objectives
Following the hook, have students take out the “Agenda”
worksheet, handed out on Day 1.
Clearly explain where the project is headed, paying
special attention to day 2. Students should have a
solid understanding of what is expected for day 2:
completion of “Which Materials are Best?” worksheet,
purchasing of construction materials, and bridge plans
should be completed.
The teacher should also tell the students the
worksheet is valuable for the project and learning
ratios, measurements, conversions, and estimation
skills. This instills in the student an understanding
of what mathematical concepts the teacher expects
him/her to learn and practice.
Ensure that students understand the importance of
obtaining the construction materials on day 2. Since
no more class time is allotted prior to the bridge
presentation and weigh-in, students must have the
“Which Materials are Best?” worksheet completed in
order to obtain materials. Without the worksheet
completed, materials, which are specific to each
project pair, cannot be given.
During the closure of class, solidify student understanding of
the bridge presentation expectations.
Ensure that all students understand the presentation
is important, yet informal. The presentation is not a
speech, yet proper mathematical concepts and language
are to be used.
Students should consider explaining why they chose
their specific design, any problems that arose during
construction, if the design is real-life applicable,
how long it took to build the bridge, and possible
changes they would make if they did the project again.
Day Two: 2
Guided Practice
While the students are working on the “Which Materials are
Best?” worksheet, the teacher should circulate the room and
provide guidance.
In regards to the worksheet, make sure it is clear
that to build a bridge out of balsa wood, ONE bottle
of Elmer’s Wood Glue must be considered in the cost of
production (i.e. a half of bottle is not possible).
Check and clarify mathematical understanding in
ratios, conversions, units, measurements, problem
solving, and geometry. Ask open ended questions that
lead students to think critically about their designs
and choice of materials. Is that enough materials to
build your design? How come you think that design is
strong? Is your design going to be easy/difficult to
build? Are there any construction techniques you see
that can make building easier? Can you buy more
inches of straws or balsa wood given the budget
restriction; is your answer reasonable? (Question
Strategies)
Handout materials specific to each project pair as groups finish
the “Which Materials are Best?” worksheet.
Day Two: 3
Closure
Model the construction of a few pieces of a bridge.
Show and ask for suggestions about pinning straws and
gluing balsa wood together. The teacher can
demonstrate his/her and the students’ techniques,
providing the class with construction suggestions.
Also, while demonstrating the construction, mention
why some techniques may prove to be stronger than
others.
As students leave the last class before the project is
due, ensure the importance of neat, thorough
construction. Mention that previous successful
bridges always have tight, snug constructions between
beams and ties. In order for a bridge to win, it must
excel in all areas.
Day Two: 4
Independent Practice
Students are given a week to complete bridge construction and
prepare a brief presentation.
Students should discover obstacles during bridge
construction that challenge their problem solving
skills. Students should note any mathematical
occurrences during the week and be prepared to share
them with the class (i.e. symmetry techniques,
problems that had to be overcome, structural or
measurements issues). If questions occur during the
construction week, students are encouraged to ask the
teacher during school or via email.
Day Two: 5