La plate-forme collaborative de bricolages scientifiques et pédagogiques


  • Warnung This pendulum works only by direct sunlight.


    (1) Put a roll of black paper in the test tube. Fill the test tube with water, then insert the small tube inside. Push very well the stopper and wipe off any spilled water.


    (2) Screw the candy bottle on its cap. The test tube should not touch the sides of the bottle. Fix the pendulum on its stand by placing two paper clip "bars" both sides of the cross junction.


    (3) Place the mobile against the Sun and set its angle so that the reflector is perfectly perpendicular to the Sun (the shadow of the winged nuts should be at the base of the metal rods).


    warning If necessary, add a little water through the hole on top of the ping-pong ball so the pendulum is nearly tipping over (you can use a piece of small tube and suck some water in, keep the water in by closing the top hole with your finger until you release it in the ping-pong ball).


    warning If the mobile tips forward but does not return it is often caused by a too heavy ping-pong ball. Try to empty a little bit the ping-pong ball.


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  • How does it work ?


    Thanks to the greenhouse effect and absorption of sunlight rays by the black colour, the water warms up in the test tube.


    The water expands and climbs along the tube towards the ping pong ball.


    The weight balance is changed and mobile tips over.


    The test tube in then no more in the focal point. It cools down and a contraction is created.


    Water flows back to the test tube and the weight balance is changed again. The mobile tips back.


    The cycle can now start again.

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  • Here is a small video the solar pendulum in action.


    The rythm of its moves is variable, but never very fast.

05.07.2012 : gdelac
En 2012 à Lutry, des élèves de 8e année ont réalisé le mobile solaire avec le soutien d'Info-Energie (Service de l'énergie du canton de Vaud).   Ils ont créé un panneau d'information pour illustrer leur bricolage lors d'une exposition organisée à l'attention des autres élèves du collège ...Lire la suite
21.01.2011 : al78
Bonjour, Nous avons effectué cette objet dans le cadre des stages WINS à la Haute l'Ecole d'Ingénieurs et de Gestion du canton de Vaud. Ces stages ont pour public des jeunes filles de secondaire (8-9ème) qui viennent comprendre les métiers de l'ingénierie. Ce mobile a été très apprécié dans sa...Lire la suite