Hi! I apologize for adding to this subject, but I can't resist to
pose a related problem, to be treated with or without those so
called "frame-related forces". Assume an experimenter in a closed
cabin, but neither in free fall nor rotating, but hanging and
oscillating like a pendulum (here, in the gravitational field of
the earth). This experimenter wishes to predict the behavior of
a little pendulum which he has. In first approximation you may
neglect the mass of his pendulum as compared to the mass of the
cabin and everything in it. As a second problem: how would the
"laws of motion" of his pendulum change if he himself, who is fat
and weighs 100 kg, is impatient and moving around irregularly in
the relatively light aluminum cabin? Good luck. Emilio