Stanford Science Bus
Science Olympics: Popsicle Bridges
Preliminary Lesson Plan / Worksheet
January 17, 18, 2011
Ages: Grades 2nd-5th
Adapted from Paul SanGiorgio
Summary: The first event in the Science Olympics this year will be the classic popsiclestick bridge.
This lesson is scheduled to occur over two class-days. The goal for week 1 will be to (i)
introduce students to the Science Olympics, (ii) have student make a preliminary sketch
of their bridge, (iii) build a small prototype to span 3 inches (students may use 20 sticks).
We may test bridges if time permits, but given that we only have one more day, any extra
time should be used to start building the larger bridge.
Week 2 will focus on full bridge construction where each student pair can use up to 100
popsicle sticks to construct a bridge spanning 1 foot. Student bridges will be judged at
Stanford during the Science Olympics on the basis of the number of pennies they can
hold in bucket suspended from the center of the span.
Materials
>Worksheets
>Popsicle sticks (120 x number of groups of 2)
>Non-Toxic Glue
>A glue gun
>A bucket and strap, to test bridges for the first week
> Atleast 200 hundred pennies
> Masking tape (to tape down edges of the bridge)
> Example Bridges
Notes
The glue we are using is somewhat expensive (about $3/ bottle), but dries quickly and is
pretty strong. It can be purchased on the Internet, or at Michael's.
Introduction
Since this is the first week of the quarter, our first order of business is to get the kids
PUMPED for the Science Olympics. This is a pretty easy task, since most of them have
either done it before or have heard about how much fun it is. Start off by asking the kids
what projects they've done in the past, what they thought was fun, etc. etc.
Summarize worksheet. Ask them why people build bridges? What makes a good bridge?
What gives it strength? What are some basic design features that we all bridges should
have?
Mini Project (week one)
Before building our “big” bridges, we're going to do some design testing. What are the
reasons for doing this? Can they think of other instances when people make smaller, or
more simple versions first? This week, we will build prototype bridges out of 20 popsicle
sticks. The bridges only need to span a distance that is just a bit longer than a popsicle
stick, so their bridges will need 2 segments. The idea here is not to build the greatest
bridge ever, but just to get some basic ideas straight. There will be a few demo bridges
that the kids can look at for inspiration.
Use clamps and hot glue gun to construct the bridges ore quickly, and try to wrap up the
building stage with about 15 minutes left, for testing. Hopefully, the normal bucket and
strap will suffice to test these mini-bridges, but if not, we will improvise. Make sure to
point out what went wrong with the bridges as they break.
Final Project (week two)
The last week will be spent on building the bridges that will be used at the Science
Olympics. Each group gets 100 sticks. In the past, we've limited the amount of glue they
can use, but this time I think we will just try to discourage abuse instead of assigning
each team a bottle.
SCIENCE BUS: Popsicle Stick Bridges
Worksheet
Please Write Your Name:
(1) Can you name this famous bridge? Why do you think it was built?
Answer: The Golden Gate Bridge (construction began in 1933), connecting San Francisco to the Marin Peninsula to the
North. At the time, the only way to get across San Francisco Bay was by ferry, which was causing quite a bit of
boat traffic in the bay.
(2) The length of a bridge is the distance it covers from one side to the other. A bridge’s
span is the distance of between the points where a bridge touches the ground.
Which is longer: the bridge’s Length or its Span?
Answer: Length
Take your best guess at estimating the Span of this bridge (how many feet long do you think it is)?
Answer: 4,200 feet
(2) Can you identify what the following small and large bridges have in common? (Hint: what
shape do you see most often?) Trace the shapes that you see.
Did you see all the triangles? Why do you think that shape is strong?
Answer (tutors may want to discuss independently in small groups as appropriate but it is likely the answer is too
complex to hold students attention at the beginning of the session. Simply note the importance of the triangle as
a shape in bridges, particularly equilateral ones, and get straight to construction):
For independent group discussion: Two major stresses that act on the bridge materials are (i) compression and (ii)
tension. For triangles, a downward force causes some of the triangle to be in compression while some of the
shape is in tension. Triangles are unique because they cannot change shape without a change in the length of one
of its sides. Therefore, a force applied anywhere is distribute to all three beams, which actually have a great deal
of compressive and tensile strength (even our popsicles sticks won’t stretch like silly putty or compress like a
string). If the joints of the triangle hold, the tensile and compressive strength of the beams must be overcome
before a structural failure occurs. By contrast, think of potential structural failure of a rectangle. Here a force
could meld it into a trapezoid without distributing the force across to the tensile or compressive strength of the
beams. With a rectangle, the structure can fail before the material does.
Use this page to draw a blueprint of what your bridge will look like. Feel free to experiment with
some sticks to see how they might fit together. Remember you only can use a total of 100 t
sticks in your final design