10/05/18 claire.marrache 1 0
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Kinetic Friction : the Timoshenko Oscillator
Réalisation Margaux Khalil (École Estienne), Julien Bobroff et Frédéric Bouquet (Laboratoire de Physique des solides, Université Paris-Sud et CNRS). Toutes les informations et les autres projets sur opentp.fr
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Niveau : Moyen
1 jour
Measurement of the coefficient of kinetic friction
![](https://opentp.fr/app/wp-content/uploads/2018/02/openTP_principles_mecanique-1.png)
Principe physique
Friction is a complex phenomenon that is of paramount importance in everyday life. We present an easy-to-build and inexpensive experiment illustrating Coulomb’s law of kinetic friction. The socalled friction, or Timoshenko, oscillator consists of a plate set into periodic motion through the competition between gravity and friction on its rotating supports. The period of such an oscillator gives a measurement of the coefficient of kinetic friction \( \mu_k \) between the plate and the supports. Our prototype is mainly composed of a motor, LEGO blocks, and a low-cost microcontroller, but despite its simplicity, the results obtained are in good agreement with values of \( \mu_k \) found in the literature.
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Arduino
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Capteur à effet Hall
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Poulie
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Moteur
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Legos
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Bricolage général
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Colle
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Fils connecteurs
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Composants divers
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Aimants
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PVC tubes
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Slabs (various materials)
Matériel
For more details : « A study of kinetic friction: the Timoshenko oscillator », R. Henaff, G. Le Doudic et al., American Journal of Physics, 86 174 2018 (https://doi.org/10.1119/1.5008862)
![](https://opentp.fr/app/wp-content/uploads/2018/05/DSC02671_small.jpg)
Build a set-up in which two PVC cylinders are made to rotate in opposite directions by a motor and a gearbox.
![](https://opentp.fr/app/wp-content/uploads/2018/01/openTP_student3_bricolage_papier1-1.jpg)
Build a plate of the desired material. The plate will be placed on top of the rotating cylinders. Tune the length accordingly.
![](https://opentp.fr/app/wp-content/themes/darfuino/includes/pics/question_1.png)
Switch the motor on and place the plate on top of the cylinders. What happens? Can you explain the plate motion?
![](https://opentp.fr/app/wp-content/uploads/2018/01/openTP_student2_programme2-1.jpg)
For a quantitative measurement : place the magnets on the plate and measure the periodicity of the motion via the Hall sensor.
![](https://opentp.fr/app/wp-content/themes/darfuino/includes/pics/question_2.png)
Does the period vary with the rotation speed of the cylinders?
![](https://opentp.fr/app/wp-content/themes/darfuino/includes/pics/question_1.png)
Does the period vary with the materials used (either for the cylinders or the plate)?
![](https://opentp.fr/app/wp-content/uploads/2018/01/openTP_student3_brico1-1.jpg)
Bonus: you can try the same experiments by placing the cylinders in liquid nitrogen first to cool them down.
![](https://opentp.fr/app/wp-content/themes/darfuino/includes/pics/question_2.png)
Does the period vary with the temperature?
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