Question

A boy sitting on the topmost berth in the compartment of a train which is just going to stop at a railway station, drops an apple aiming at the open hand of his brother sitting vertically below his hands at a distance of about 3 metre. The apple will fall
A.Precisely on the hand of his brother
B.Slightly away from the hand of his brother in the direction of motion of the train.
C.Slightly away from the hand of his brother in the direction opposite to the direction of motion of the train
D.None of the above

Answer 1

Hint: Train is just going to stop it means it’s speed is decreasing or its decelerating so we cannot treat train as a inertial frame of reference but once apple is thrown in air it will come under the influence of gravity, velocity of apple in the direction of the motion of train will not change as long apple stays in air

Complete step by step answer:
Let at that instant train is moving with certain velocity then everything attached with the train will move with same velocity
So when the boy drops the apple the apple will have velocity same as the velocity of train in horizontal direction
But when the apple is dropped in air it is no longer attached with the train it will move only under the influence of gravity and its velocity along horizontal will remain constant
Now for the time duration when apple is in air if we consider the motion of the apple and his brother in horizontal direction
Since his brother is attached to the train and the train is decelerating while apple is moving with constant velocity so his brother will fall behind a little bit when the apple falls and apple will be slightly away from his brother in the direction of motion of the train.

Hence Option-B is correct.

Note: Here you need to understand the meaning of “train is just going to stop” and it means train must be decelerating once you know the train is decelerating now you need to speculate the motion of the apple and train once the apple starts falling.