PURPOSE: To illustrate the Coriolis effect.

DESCRIPTION: 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.

Click here for videos of ball rolling across platform with

platform at rest, viewed in stationary frame of reference.

platform rotating, viewed in rotating frame of reference.

platform rotating, viewed in stationary frame of reference.

SUGGESTIONS: See Question of the Week #87 and Question of the Week #88 for information on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 1E30.28) See Demonstration Reference File for a host of literature discussing aspects of the Coriolis effect, including this demonstration.

EQUIPMENT: Fancy plastic disc on rotating stool base, billiard ball.

SETUP TIME: 10 minutes.

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