Whe a stone is dropped from a railway carrialge, it will fall vertically downwards with respect to earth, the accleration of the stone will be g only.Inside the carriage the stone has two acceleration : (i) horizontal acce.eration (a), due to the motion of the carriage and (ii) vertical acc. due to gravity (g). Thus the acceleration of the stone with respect to carriage is ` sqrt a^(2) + g^(2)`.