A plumb bob is hung from the ceiling of a train compartment. If the train moves with an acceleration a along a straight horizontal track, the string supporting the bob makes an angle `tan^1 (a/g)` with the normal to the ceiling. Suppose the train moves on an inclined straight track with uniform velocity, if the angle of incline is `tan^-1(a/g)`, the string again makes the same angle with the normal to the ceiling. Can a person sitting inside the compartment tell by looking at the plumb line whether the train is accelerated on a horizontal straight track or it is going on an incline? If yes, how? If no, suggest a method to do so.