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by Procheta Mallik


There are many models that demonstrate friction and still more that show energy conservation. This shows both using materials easily available at home

    • Take care while using the cutter/scissor.

    • Be careful while working with the candle and the metal rod. The rod can remain hot for a few minutes after heating it.

  1. Find two bottles of the same size.
    • Find two bottles of the same size.

    • Cut the upper portion of the bottle about 6-8 cm from the cap.

    • Use a marker to draw out a reference line, which would help you to cut the bottle.

    • Take care while using the blade. Make sure you use only a small portion of the blade to cut, to prevent any damage to the blade.

    • Now, on the lower part of the bottle, draw a reference line, about 5-6 cm from where you made your first cut.

    • Take care while using the blade.

    • Light a candle and heat a metal wire over it.

    • Press the metal wire on the bottle cap to make a hole.

    • Do this for both the bottle caps.

    • Make the hole big enough to fit the metal/wooden skewer.

    • Don't make the hole too big. The metal/wooden skewer must fit tightly.

    • Measure a distance halfway from the top of the cut portion of the bottle and mark it using a marker.

    • Use a heated metal wire and make a hole on the marking.

    • Make another hole opposite to the one you just made.

    • The metal/wooden skewer should fit through these holes.

    • Use a pair of scissors to cut two straw pieces of 2 cm each.

    • Now, at a distance halfway between the two holes you made, mark another point. Make sure it is at a distance halfway from the top of the bottle as well.

    • Use a candle-heated wire to make a hole on this marked point.

    • Make another hole right opposite the one you just made.

    • These two holes must be big enough to the straw pieces. If the hole you made happens to be too big, you can use some glue to fix it in the hole.

    • Use a piece of foam and glue it on the under side of both the bottle caps.

    • Take one end of the wooden skewer and insert it into the bottle cap as shown in the picture.

    • Insert the wooden skewer into the small hole in the bottle.

    • Once the wooden skewer is inserted through both the holes, you can insert the other bottle into the free end of the skewer.

    • Tie one end of a thread to a nut.

    • Take the open end of the thread and pass it through the straw in one of the holes.

    • Now, loop it around the wooden skewer once.

    • Pass the loose end of the thread now through the other straw

    • Holding the free end of the string, pull up the bottle-and-skewer assembly right up to your fingers.

    • Now release the assembly, and hopefully it shimmies down the string smoothly!

    • If your bottle wheel does not start rotating immediately, give it a gentle push.

    • The weight of the nut is too much.

    • The hole through which the wooden skewer is passed through is tight.

    • The alignment of the straws is off, hence, the thread isn't straight. This prevents a smooth rotation of the bottle flywheel.

    • The thread used is too smooth and/or the skewer used is too smooth.

    • The bottle cap/s is/are not inserted tightly into the skewer.

    • Why do you think we need to add a weight at the end of the string?

    • What do you think determines how fast the flywheel falls?

    • Do you think the flywheel is falling down with a constant speed? Can you measure this? Or the average speed?

    • Why have we looped the thread over the skewer?

Finish Line

Suhail Ahanger

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