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Reference Frames

  • D5-11: CORIOLIS EFFECT - BALL ON ROTATING PLATFORM

    D5-11
    Illustrate the Coriolis effect.
    Start the platform rotating slowly then roll the ball across it. The ball will roll straight in the laboratory frame of reference but along a curved path in the rotating reference frame. The direction of curvature (left or right) depends on the direction of rotation of the platform (clockwise or counterclockwise). The globe is used to relate this effect to the Coriolis effect on the earth. Using this model, rotation of the platform counterclockwise simulates the northern hemisphere while clockwise rotation of the platform simulates the southern hemisphere.
    OS12

  • D5-21: BALL ROLLING ON ROTATING DISC

    D5-21
    Show that a sphere rolling on a rotating disc will move in circles.
    The ball can be placed at the center of the rotating disc and tapped to initiate the motion or it can be loosely trapped with your fingers at about half the radius of the disc, and then released. The frequency of the circular motion does not depend on either the radius or the mass of the ball, or on the radius of the orbit, but only on the frequency of the rotating disc.
    OS12