In which of the following examples of motion, can the body be considered approximately a point object:

A. A railway carriage moving without jerks between two stations.

B. A monkey sitting on top of a man cycling smoothly on a circular track.

C. A spinning cricket ball that turns sharply on hitting the ground.

D. A tumbling beaker that has slipped off the edge of a table.

Hint:A point object is considered a small object or a dot object; it is considered a point object so as to simplify the calculations. An object can be considered as a point object when the size of the object compared to the distance covered by the object is negligible.

Step by step solution:
Consider all the options given and try to make a conclusion, in which given option the object can be considered as a point object. Let us see all the options one by one and then we will try to get to the conclusion that which option can be considered as a point object
Let us see first option,
A railway carriage moving without jerks between two stations. A railway carriage moving without jerks between two stations, in this option the distance covered by carriage is very small as compared to the distance travelled by carriage between two stations. Therefore, railway carriage can be considered as a point object.
Let us see second option,
A monkey sitting on top of a man cycling smoothly on a circular track. The size of the monkey is very small as compared to the distance travelled by monkey in the circular track. Therefore, monkeys can be considered as point objects.
Let us see third option,
A spinning cricket ball that turns sharply on hitting the ground. The size of the ball is comparable to the distance through which the ball turns sharply on hitting the ground. Hence, a cricket ball cannot be considered as a point object.
Let us see the fourth option.
A tumbling beaker that has slipped off the edge of a table. The tumbling beaker is of comparable size of height of the table through it slips. Hence, the beaker cannot be considered as a point object.

Note: We only consider any object as a point object when the size of the object is very small as compared to the distance travelled by the object. Students should always compare the size of the object to the distance which the object is travelling. While solving problems we consider an object as a point object so that the problem can be solved easily.