The train is moving at 50 m/s and Emma is walking down the aisle with 1 m/s speed in the same direction of train. The relative velocity of Emma with respect to other passengers pf the train would be 1 m/s. This is because, the train is not moving relative to them and only emma is moving at 1 m/s. If a person observes from outside, Emma would have (50 +1) m/s = 51 m/s velocity.
relative velocity when two objects are moving in same direction as oberved from outside observer:
[tex] v_{ab}=v_a+v_b[/tex]
relative velocity when two objects are moving in the opposite directionas oberved from outside observer:
[tex] v_{ab}=v_a-v_b[/tex]
