A boy of mass `40 kg` moves on a `10 m` long , `60 kg` railroad car on the smooth horizontal floor. Now the boy moves with speed `5 m//s`. (a) Find the velocity of the car with respect to the floor. (b) If the boy starts from middle of the car and reaches to one end of the car , find the distance traveled by the car. (c ) If the boy stops at the end , find the velocity of the car. (d) If the boy falls off the car at one end while walking , find the velocity of the car.