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1.9

Major VersionM

by Madhushree HS

Introduction

Beam balance is an apparatus used to measure mass of different objects by comparing it with a known mass. It consists of a horizontal beam with a support at its centre and depends on the gravitational pull on it.

In this TACtivity, we will learn to make a beam balance to measure and compare the mass of different objects using the given weights.

    • Handle the paper cutter/scissors with care.

    • If using the candle, light it with care under adult supervision.

  1. You need two plastic bottles of the same size. Take a plastic bottle. Cut the bottle in half using a paper cutter/scissors.
    • You need two plastic bottles of the same size.

    • Take a plastic bottle.

    • Cut the bottle in half using a paper cutter/scissors.

    • Repeat the above step for the other bottle.

    • Only the bottom part of the bottles are needed for this TACtivity.

  2. Place the cut bottle on the given template, such that the centre of the bottle is placed above the dot of the template. Draw three lines on the bottle, which are perpendicular to the lines on the given template. Measure and mark 2 cm, along a line drawn in the previous step, from the top of the cut bottle. Heat a metal wire/spoke on a candle flame and make a hole at the marked point. Repeat the above step to make holes on the other two lines.
    • Place the cut bottle on the given template, such that the centre of the bottle is placed above the dot of the template. Draw three lines on the bottle, which are perpendicular to the lines on the given template.

    • Measure and mark 2 cm, along a line drawn in the previous step, from the top of the cut bottle. Heat a metal wire/spoke on a candle flame and make a hole at the marked point.

    • Repeat the above step to make holes on the other two lines.

  3. Take 3 pieces of thread of equal length (~25cm). Insert each piece of thread into each of the three holes and secure them with knots on the bottle. Repeat the above steps for the other cut bottle. The two bottles will now act as weight holders.
    • Take 3 pieces of thread of equal length (~25cm). Insert each piece of thread into each of the three holes and secure them with knots on the bottle.

    • Repeat the above steps for the other cut bottle.

    • The two bottles will now act as weight holders.

    • Tie all the three threads together with a knot at the loose ends.

  4. Join the two spokes by screwing the spoke nut halfway into the threaded end of each spoke. Now, this acts as the beam. Balance the beam on two fingers to find out the centre of gravity of the beam. Identify the point at which the beam remains horizontal, when balanced on your fingers. Once you find the approximate point, identified as the centre of gravity, try balancing the beam at the identified point on one finger only. Tie a thread at the point, identified as the centre of gravity, on the spoke assembly.
    • Join the two spokes by screwing the spoke nut halfway into the threaded end of each spoke. Now, this acts as the beam.

    • Balance the beam on two fingers to find out the centre of gravity of the beam. Identify the point at which the beam remains horizontal, when balanced on your fingers. Once you find the approximate point, identified as the centre of gravity, try balancing the beam at the identified point on one finger only.

    • Tie a thread at the point, identified as the centre of gravity, on the spoke assembly.

    • Use insulation tape near the thread, to secure it firmly at the desired position.

  5. Place the weight holders at the extreme ends of the "beam" and use insulation tape to secure them. Try to balance the two weight holders. If the beam is not balanced with empty bottles as seen in the picture, use layers of insulation tape at the extreme ends of the spoke as counter weights to balance the beam.
    • Place the weight holders at the extreme ends of the "beam" and use insulation tape to secure them.

    • Try to balance the two weight holders.

    • If the beam is not balanced with empty bottles as seen in the picture, use layers of insulation tape at the extreme ends of the spoke as counter weights to balance the beam.

    • A balanced beam gives an accurate result.

  6. The balanced beam can be seen in this picture.
    • The balanced beam can be seen in this picture.

  7. Play with your beam balance using the given nuts. Add different number of nuts on either side of the weight holder and observe. 1 nut weighs 1 g each. Use the nuts to weigh various objects.
    • Play with your beam balance using the given nuts. Add different number of nuts on either side of the weight holder and observe.

    • 1 nut weighs 1 g each. Use the nuts to weigh various objects.

    • For example, place a stone on one side of the balance and continue to add nuts to the other side, until the weight holders are at the same horizontal level. Count the number of nuts in the weight holder and record it, which will be the mass of the stone. Verify the mass by weighing it on a weighing scale.

    • If the empty weight holders are not at the same height while balancing them, then ensure -

    • All the three holes are at the same level of 2 cm from the cut end of the bottle.

    • The threads tied are of the same length.

    • The bottles are hung at equal distances from the centre of the spoke beam.

  8. Variation 1: Bias the beam balance by adding weight to the container/weight holder. Variation 2: Bias the beam balance by adding thick binding wire to one of the beams.
    • Variation 1: Bias the beam balance by adding weight to the container/weight holder.

    • Variation 2: Bias the beam balance by adding thick binding wire to one of the beams.

    • To learn more about this variation, go to Measure Mass - Beam Balance (Variations).

Finish Line

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