Since I wanted this to be a new thread, this is a reposting with a new
title. Martin already responded under the first posting with the
title "Mechanical Problem," which was unfortunately already a existing
thread from last year.

This problem was discussed in s.p.r but since it is not specifically
relativity, I thought I'd ask for help here.

The question is whether the same forces are at play in a projectile
launched from a moving source to a co-moving target as with a
stationary source and target.

A thought experiment illustrating the problem would be that there are
two train tracks parallel to each other with one train on each
travelling in the same direction at the same speed. An archer on one
train aims at a target on the other train which is perpendicular to
the archer and shoots an arrow at the target. No air/wind effects,
etc. The arrow hits the bullseye of the target. Same scenario with
stationary trains. Are the mechanics different? It has been
suggested that in the moving scenario, momentum is imparted by the
train to the arrow in the direction of travel of the train and when
the arrow is shot it is not really travelling perpendicular to the
train, but rather at an angle because of the added momentum. Further,
the path to the target is longer because of the movement of the train
that the target is on during the flight time of the arrow. However,
these effects offset each other so the arrow still hits the target.
In the stationary scenario, since the train with the archer is not
moving, no forward momentum is imparted to the arrow. So the
conclusion would be that although the arrows in both scenarios hit the
target, the mechanics are different.

The reason this was first discussed in the s.p.r group was to consider
replacing the arrow with a light source to see if the result is
different since supposedly movement of the source cannot change the
velocity of light, nor impart any momentum to it.

Thanks,
Vern