In a message dated 6/30/2009 9:55:41 AM Eastern Daylight Time,
maddox@physics.Auburn.EDU writes:
From: WC Maddox
Relativistic mass just won't go away. In the article by Gary Oas (On the
abuse and use of relativistic mass) arguing against the use of
relativistic mass there is a question that students were asked. It
amounts to weighing yourself on a spring scale at rest with respect to
the Earth and then weighing yourself using the same scale while moving
relative to the Earth. Would you, at least in principle, detect a change
in the scale reading? The answer in the article was no on the grounds
that mass does not increase with velocity.
In an article by Bernhard Rothenstein (Relativistic velocity
transformation as a genitor of transformation equations) there is a
setup involving a two pan balance. The pans are on those frictionless
rods found in introductory physics texts. There are given equal speeds
(V) in opposite directions. At time t (center observer time) equal
masses are placed on the pans which are equal distances from the center.
The apparatus will remain balanced from the point of view of an observer
in the center. What about from the point of view of an observer (A)
traveling with one of the masses? According to the article, if A uses
the relativistic velocity addition formula to calculate the speed of the
other mass (B) and uses this to find the length of arm B, then observer
A finds arm B is shorter than arm A. According to the article A finds
that B is moving from the center with a speed less than V so distance
traveled by B is less than distance traveled by A. To remain alanced,
mass B would have to be larger by an amount given by the relativistic
mass formula.
Did one author make a mistake? Does it matter whether it is a spring
balance or a two pan balance? Are both authors wrong by not bringing in
general relativity?
End Message
))))))))))))))))))))))))
Measurements in your own frame (absent acceleration) produces the same
results regardless of what an observer in a different inertial frame measures
your velocity relative to him to be. While he sees your clock running
slower, to you nothing has changed.