A bird is flying towards north with a velocity 40km/h and a train is moving with a velocity 40km/h towards east. What is the velocity of the bird noted by a man in the train?

To find the relative velocity of bird w.r.t train, superimpose velocity−V→T  on both the objects. Now as a result of it, the train is at rest,while bird posses two velocities −V→B  towards N and −V→T  along west.Where, −V→B  = Velocity of bird       −V→T  = Velocity of train.|V→BT|=|V→B|2+|−V→T|2[By formula, ∴  θ=900 ]=402+402=402km/hr  North−West