5.2 Force Needed for Circular Motion
Rotating Frames of Reference


 start.gif (693 bytes)

This applet simulates the case of an object being thrown with an initial horizontal velocity by a person standing at the edge of a rotating platform. As discussed in chapter 5 Section 2, without a centripetal force the object will keep moving in a straight line. This concept is illustrated in the right frame of the applet. This frame shows the resulting motion as seen from the top, by an observer above the platform and stationary with respect to the ground.  The left frame shows a top view of the motion from the perspective of a person on the platform. Note that the platform does not rotate in this frame!  Since the platform's frame of reference is a non-inertial (accelerated) frame, observers on the platform experience apparent forces that are not observed from the ground (the inertial frame of reference).  One of these fictitious forces is the centrifugal force shown in blue and discussed in the book in Section 5.2, the other is called the Coriolis force.  The Coriolis force is represented in magenta in the simulation and is not discussed at this level.
FUN@LEARNING.PHYSICS, by Mark Sutherland