In which of the following examples of motion, can the body be considered approximately a point object.
(a) A railway carriage moving without brakes 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 table.
Answers
Hey mate !!!
The consideration of a point objet is based on the type and number of forces acting on it.
In the given question ;
A tumbling beaker can be considered as a point object as the number of forces acting on it will not depend on it's shape and modulation.
Alongwith that ;
The train without brakes can be also taken as a point object as the friction and other resistive forces acting on it will work on it as a whole.
(a) The railway carriage moving without brakes between two stations so the distance between the two stations is considered to be as large as the size of the train. Due to this reason the train is considered as a point object.
(b) The monkey can be considered as a point object because the value of the distance covered by the circular train is much greater.
(c) The way the ball turns is not smooth because of this reason the distance covered by the ball is not large enough in a reasonable amount of time due this the spinning of a cricket ball that turns sharply on hitting the ground cannot be considered as a point object.
(d) The distance covered by a tumbling beaker that has slipped off the edge of table cannot be considered as a point object because the distance covered is very less not enough to be considered as a point object.