Tuesday, January 10, 2012


Recently, students in grades K-3 created Lego based see-saw models. As part of this inquiry, they determined that position and weigt determined how well a see-saw stayed balanced. They identified the fulcrum and were able to explain how weights should be placed to keep the plank balanced.

From there, some classes completed a see-saw challenge. They used paper towel rolls, pennies and craft sticks to apply the skills they learned from their Lego exploration. Would you like to try it at home? You can! I took this specific actitivity from one of my favorite scientific dogs, Ruff Ruffman! Even teachers can take an idea or two from PBSKids!


  1. Get what you need:
    • Seesaw platform (e.g., ruler, paint stirrer, large craft stick, or yardstick)
    • Tape
    • Toilet-paper tube
    • Weights (e.g., pennies or metal washers)
  2. Build your seesaw: Tape the toilet-paper tube to the table as shown in the illustration. This is your fulcrum, the point where your platform rests. Then balance your seesaw platform on top. Adjust the platform until it's parallel to the tabletop.
  1. Try these challenges: The goal of each challenge is to have the platform be level, sitting parallel to the tabletop. Once it's level, we say it's balancing. Before you start, here are three hints.
    1. It's okay to have the platform touch the table while you're working on a challenge.
    2. It's okay to move the platform and change where it touches the fulcrum.
    3. The weights don't have to be stacked or placed together on the platform.
    Challenge 1: Put three weights on each end of the platform.

    Challenge 2: Put three weights on one side of the platform and six weights on the other.

    Challenge 3: Set the platform so one end sticks out twice as far beyond the fulcrum as the other end. Add weights until the platform is level.

    Challenge 4: Put ten weights on one end of the platform and NONE on the other end.


With balancing, it's not just weight that matters. Position matters, too. Two things help keep your seesaw balanced: weight and distance. Weight is how much weight there is on each side of the fulcrum. Distance is how far each weight is from the fulcrum. Together, weight and distance create leverage. That's why, with your seesaw, you can balance a stack of pennies close to the fulcrum on one side with just one penny far from the fulcrum on the other side. Even though the single penny has only a little weight, it's far from the fulcrum, giving it a large amount of leverage.


  • Make a multi-platform seesaw. See what kind of wacky balance systems you can make by adjusting the positions of the platforms and the number of weights.
  • Make a mobile using string, pencils, and small objects. Adjust the weights and position of the strings so that the pencils hang parallel to the floor.

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