144
Activity 2: Base isolation with student worksheet*
acting on the building, it won’t move. Base isolation
is separating the building from the ground so that the
earthquake can’t affect it.
If you lay a toy car or a skate on a cardboard sheet
and yank the cardboard back and forth like the
horizontal motions of an earthquake, what happens?
The car will not slide as much as the cardboard, but it
will still move slightly back and forth. Those wheels
on the car and skate “isolated” the top part from the
earthquake!
But how do we do that with a big building? In reality,
engineers don’t use big wheels. Instead, they use a
special material between the columns of the building
and its foundation. This supports the building so that it
can stand, but it lets the “ground” move from side-to-
side underneath it.
Objectives: Observe how base isolation protects
buildings during an earthquake.
Grade Level: Middle School
Time: 30 Minutes- 1 Hour
Problem: How can we keep a building from
shaking on our shake table?
Introduction:
Why do you need to wear a seat belt? If you are
in a car going 70 mph and slam on the brakes, you
will continue to go at 70 mph (and through the
windshield!) unless something like a seat belt stops
you.
Newton’s rst law states that a body in motion will
stay in motion and a body at rest will stay at rest
unless acted on by an outside force. This is called
inertia. It is the tendency of something to stay the
way it is.
The law of inertia is important when talking
about buildings in an earthquake. A building can
be thought of as a large mass, and according to the
law of inertia, it wants to stay at rest and remain
motionless unless acted on by an outside force. In
an earthquake, the bottom parts of the building move
and the upper parts of the building don’t because of
inertia. This is called inertial force. This puts a lot
of stress on the parts that make up the building. It
is this inertial force that engineers have to try and
minimize when designing buildings.
One of the ways that earthquake engineers protect
a building is to use the inertia of the building to their
advantage. If they can keep the body from moving,
then the top oor won’t move either! So, if an
engineer can nd a way to keep the earthquake from
Materials:
(see following pages)
Shake table
Base isolation attachment
Masses on rods
Vocabulary:
Inertia, inertial force, base isolation, friction
* Worksheets by: Leslie Bucar, 7-12 Science Teacher, Fond du Lac Ojibwe School, B.S. Biology,
B.A.S. Teaching Biology, B.A.S. equiv Teaching Chemistry
Dan Johnson, 7-12 Math Teacher, Fond du Lac Ojibwe School, B.A.S. Teaching Math