NCSO 2013-2014
Simple and Compound Machines
MAKING A FIRST CLASS LEVER
In the Science Olympiad competitive event “Simple Machines” Middle School (Division B) must make a
first class lever to determine the mass of an unknown weight when given a known weight. High school
(Division C) must additionally make a class 2 lever to attach to the class 1 lever. The larger lever shown in
the images is the Class 1 lever. The smaller is the class 2. Instructions are given for the class 1 lever. Class
2 is made the same way, but with the fulcrum (straw) on one end instead of in the center.
MATERIALS:
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Two 20 oz or larger Styrofoam cups
1 bamboo skewer or chopstick (round!)
1 drinking straw
1 paint stick
1 metric scale (a ruler with no numbers)
1 small paperclip or penny (ballast)
High school also needs a push pin and second set of materials above
Tools: scissors, scotch tape, packing tape, hot glue, and a sharpie
INSTRUCTIONS:
1. Find the center of your paint stick and hot glue a piece of
straw to it. This is your fulcrum point.
2. Turn the paint stick over and tape a metric scale to it
with scotch tape, line up one of the larger marks on the
center of the straw. You may need to tape 2 scales
together if your paint stick is longer.
3. Use a sharpie to number your marks. Start in the center
with “0”, and increase as you go outwards in each
direction. When you are done marking your increments,
“laminate” the scale onto the paint stick with packing
tape.
NCSO 2013-2014
Simple and Compound Machines
4. Line your cups up and poke the skewer through the top of one, thread it
through your straw fulcrum, then poke it through the other cup. You need
to be very close to the top of the cup so your lever will be high enough the
weights don’t hit the ground.
5. Flip the lever over between the cups so you are looking at
the bottom. Is it balanced? If not, slide a paperclip or coin
around on the side that is too light until you find the spot
where it is closest to balanced and tape it down. This won’t
be perfect, you just want to be close.
6. Now flip your lever back over, it should be relatively balanced. Time to test it out! See the
additional worksheet “A Visual Representation of a Math Equation” for help with calculating the
unknown mass.
7. Always be on the lookout for sources of error. This gives you the general concept, now try to make
it better!
The Class 1 lever (Middle School):
The Class 2 lever in series with the Class 1 lever (High School):