Theory of Relative Motion
Tower Chen
University of Guam Guam
Zeon Chen
U.S.A.
Abstract
If there are two trains at a platform, one train
remains stationary at the platform and the other train
moves on a straight railroad with a constant velocity
relative to the platform. An observer on any train
cannot tell which train is actually moving without
referring to the platform. Such experience makes us
believe that all motions are relative without
reference point. We generalize this problem into four
cases for discussion. (1) If there is relative linear
motion between two singlepointobjects, an observer
on either object will have the same descriptive motion
of the other object by assuming that he is stationary.
(2) If there is relative circular motion between two
singlepointobjects, an observer on either object
will have the same descriptive motion of the other
object by assuming that he is stationary. (3) If
there is relative linear motion between two pair of
singlepointobjects connected together, an observer
on either pair of objects will also have the same
descriptive motion of the other pair of objects by
assuming that he is stationary. (4) However, if there
is relative circular motion between two pairs of
singlepointobjects connected together, an observer
on either pair of objects will have different
descriptive motions of the other pair of objects by
assuming that he is stationary.
Thus, the Theory of
Relative Motion is concluded: There is no preferable
pair of inertial frames to describe the linear motion
of an object, but there is a preferable pair of
inertial frames to describe the circular motion of an
object. They can tell which pair of objects are in
circular motion only through kinetics not through
dynamics, so circular motion is absolute. This result
is different from what we expect. This paper utilizes
the locus toolcommand in the Cabri Geometry II Plus
Program to illustrate this theory.
