In which of these cases, a body can be considered as point object:
(a) a train moving without jerks between two stations.
(b) a monkey sitting on top of a man cycling smoothly on a circular track.
© a spinning cricket ball turns sharply on hitting the
ground.
(d) a tumbling beaker slipped off the edge of a table.
(a) Since the motion of the train between two distant stations is smooth throughout so keeping in view the long distance covered between the two stations in reasonable duration of time, the size of the train is neglected and it is considered as a point object.
(b) The distance covered by the monkey in reasonable duration of time is more so the monkey is considered as a point object. Since its size is smaller.
© Since, the turning of the ball is not smooth but sharp so the distance covered by it in reasonable duration of time is not large so this ball cannot be treated as a point object.
(d) Since the beaker is tumbling and then slips off. So, the distance covered by it in reasonable duration of time is not large, so it is not treated as a point object.