looks right to me , pretty good excellmanship also.
that is exactly what a spring would do , a spring
would be compressed by the mass slowing the pipe to a stop.

if the spring stops the mass in 0.5 seconds it requires 8000N
to do that , it then has 8000N stored force to push the mass
away again accelerating the pipe in the opposite direction.

if the spring stops the mass in 1 second , it requires 4000N
to do that , but that would only slow the pipe down , it then
has 4000N stored to push the mass away with stopping the pipe.

so if the turn is increased in lenght to 80 meters the
pipe would stop , and the mass would still have a speed of 40 m/s when it exits the turn.

correct?

I think you had also mentioned that earlier.
so you were right about that.



3/4 inch of dust build up on the moon in 4.527 billion years,LOL and QM is fantasy science.