Question

why is the motion of the train is called accelerated motion ?

Answer 1

no the motion of 3 is not necessary accelerating it maybe or may not be accelerating sometimes it moves with constant velocity however when it moves with constant speed remember I am saying speed OK when it moves when it Run with constant speed it may change its direction along the track and when an object change its direction its velocity gets changed and we know that the change in velocity with respect to time is acceleration hence we can say that the train is

Answer 2

There are 3 types of sipped involved in the motion of the train.

Initial speed
Crest speed
And terminal speed

Acceleration motion:
It is due to the continuous momentum applied