I was playing a game at a friends house and when we were done I turned the
power off and opened the tray. The CD was still spinning and I grabbed it
and put it in the case. He cringed and says that that puts a lot of stress
on the spindle. Argument ensues.
If I have a bicycle wheel with pedals attached to the center and I set this
in motion, I can stop it by applying force to the pedals, or I can stop
this by applying force to the rim. It is easy to see which case I'm more
likely to break the pedals.
the freely spinning CD is the same thing. the force is applied to the edge
and the majority of it goes to stop the cd's rotation. What is left over
for the spindle is only the enough force to stop the spindle. The spindle
with a low mass and short radius has very little in the way of rotational
inertia so the forces on the spindle are slight.