cal characteristics, including the design and the building materials.
Resonance is a buildup of amplitude in a physical system that occurs
when the frequency of an applied oscillatory force is close to the
natural frequency of the system. In the case of an earthquake, the
ground shaking may be at the same frequency as the natural frequency
of a building. Each vibration in the ground may come at or
dangerously close to the natural frequency of the structure.
Ask the class to hypothesize what would happen when buildings of
two different heights, standing next to each other, resonate from an
earthquake. Wiggle the BOSS model so that assemblies 2 and 3
vibrate greatly, and let students see how buildings hammer together
during powerful earthquakes. If you have some images of this effect
from actual earthquakes, show them now.
Entice students to further investigation by leaving them with the
question: “How could you add structural elements to reduce resonance
in a building?”
ADA P T A T I ON S AND E X T E N S I ON S
1. Tell students that one way to protect a building from resonating
with an earthquake is to isolate its foundation, or base, from the
ground with devices much like wheels. This technique is called base
isolation. Structural engineers are now developing the technology to
place buildings on devices that absorb energy, so that ground shaking
is not directly transferred to the building.
Invite students to add standard small wheels from a
hardware store to their models as an illustration of one of
the many base isolation technologies, or add wheels to
your own BOSS model, then shake the table. Better yet,
place the model in a low box or tray and shake it. Then
take out the model, fill the box with marbles or BBs, and
replace the model on this base. Now shake the box.
Challenge students to come up with other base isolation
techniques.
2. If any of your students have studied harmonic motion in
a physical science or physics class, challenge them to
explain how the BOSS model is an example of an inverted
pendulum.
3. To help students connect the numbered rod assemblies
to actual buildings, make paper sleeves and decorate them
to resemble buildings in your area. At some point in the
lesson, slide the sleeves over the rod assemblies to show
how buildings can collide, or hammer against each other,
during an earthquake.
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