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Minor Versionm

by Procheta Mallik


By making a see-saw out of a ruler, we may experiment by placing various weights at varying distances from the fulcrum and playing a balancing game!

    • Handle the paper cutter with care

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  1. Join the two 15cm rulers end-to-end to form a 30-cm-long ruler.
    • Join the two 15cm rulers end-to-end to form a 30-cm-long ruler.

    • There is a slight gap/offset (~0.5 cms) between the 0 cm marks of each of the rulers

    • Place the first ruler on sandpaper and gently scrape the end of the ruler till the 0-cm mark.

    • Similary, scrape the second ruler up to the 0-cm mark using sandpaper.

    Vishal 2606:

    (1) Edit the parts - pencil....

    (2) Let's give 10 ring magnets for them to play around.

    (3) Specify the thickness of the grove.

    (4) Can we take a new ruler for photos so that the reading is visible?

    Procheta Mallik - Reply

    • Now join the two scraped rulers end-to-end, on the "0-cm" side.

    • Measure the length of the ice cream stick, and using a marker, mark the centre of the ice cream stick.

    • Flip the two joined rulers and apply glue.


    (1) Why does the size of styrofoam need to be exactly 3.5 cm on one side?

    (2) Let's give other options for material like rubber or thermocol. Include them in the photos.

    Procheta Mallik - Reply

    • Place the centre of the ice cream stick on the glued surface at the joining line of the rulers.


    The whole purpose of this tactivity is to have children measure the mass and distance from fulcrum. I don't see it mentioned anywhere, neither in the steps nor observations.

    Procheta Mallik - Reply

    • Using a cutter, groove the mid-line of the ice cream stick .

    • The groove made acts as a balance for the ruler when placed on the cardboard strip.

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    • Take the foam piece; you may also use a rubber piece or thermocol piece of similar size (~ 5cm x 1.5cm x 0.7cm). Using a paper cutter make a groove along the length of the centre of the foam.

    • Cut a thin cardboard strip (~ 4cm x 1cm) and place it on the rubber groove .

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    • Apply glue on the cardboard sheet .

    • Place the scale on the glued cardboard piece such that the groove on the ice cream stick sits on the cardboard .

    • The ruler should now be balanced.

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    • Take one ring magnet and place it a few cm from the centre.

    • Place another magnet directly below the first one such that it sticks there, thanks to the magnetic attraction.

    • Similarly, place another two ring magnets at the other side of the ruler. You have created your see-saw! Move the magnets around to balance the scale.

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    • Play around with the magnets given, and place any number at any location on one side and try and balance with a different number or at a different location on the other side.

    • Place one magnet on top of the first ruler.

    • Place another magnet at the bottom of the first ruler .

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    • The first ruler now has 4 magnets. Try to balance the ruler by moving the magnets.

    • Try various combinations of weights and distances on either side to achieve balance!

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    • The cardboard piece should be nice and firm

    • The groove on the scale needs to be deep enough so that it doesn't slip when placed on the cardboard strip

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    • While you play with different no. of magnets at different locations, note down the following when the scale is balanced: No. of magnets (n) and their distance (d) from the centre.

    • Can you identify a pattern as to when the scale is balanced?

    • Now, multiply each F (no. of magnets in our case) with its corresponding d. Add all the (n x d) on one side of the ruler and compare that with the sum of all the (n x d) on the other side of the ruler. Did you discover anything?

    • Think about how this might also help you in maths class when you study factors and LCM/HCF!


    The observation questions do not lead towards the objective of the tactivity.

    Procheta Mallik - Reply

Finish Line

Suhail Ahanger

Member since: 05/02/2017

3,665 Reputation

55 Guides authored


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