I am currently studying Kinematics and there's a little bit confusion about the definition of point object given in my course book NCERT(it is a standard textbook in India) which is as follows :
This approximation (of point object) is valid so far as the size of the object is much smaller than the distance it moves in a reasonable duration of time.
But when I started solving the exercise, one particular question requires the learner to differentiate weather an object in a particular situation can be considered as point objects or not and there are two options which cannot (as far as I think) be differentiated into any of these categoriea by considering the definition, which are :
(c) a spinning cricket ball that turns sharply on hitting the ground.
(d) a tumbling beaker that has slipped off a table.
Please give an proper and elaborated definition of point object and also the usage of this approximation in physics.
Also, please clarify the advantages of this definition.