(a) The railway carriage moving without jerks between two stations, so the distance between two stations is considered to be large as compared to the size of the train. Therefore the train is considered as a point object.
(b) The monkey may be considered as point object because value of distance covered on a circular track is much greater.
(c) As turning of the ball is not smooth, thus the distance covered by the ball is not large in the reasonable time. Therefore the ball cannot be considered as a point object.
(d) Again a tumbling beaker slipped off the edge of a table cannot be considered as a point object because distance covered is not much larger.