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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

  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.

    • 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.

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

    • 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.

    • 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 .

    • 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.

    • 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.

    • 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 .

    • 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!

    • 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

    • 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!

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