Question

Which will have least inertia?
A. A football
B. A needle
C. A thread
D. A refrigerator

Answer 1

Hint: Remember Newton's first law of motion and try to establish the relation of inertia with the mass of the object. Mass is that quantity that is solely dependent upon the inertia of an object. A more massive object has a greater tendency to resist changes in its state of motion.

Complete step by step answer:
According to Newton's first law of motion or law of inertia, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.Now, Mass is that quantity that is solely dependent upon the inertia of an object.The more inertia that an object has, the more mass that it has because a more massive object has a greater tendency to resist changes in its state of motion.
Inertia is directly proportional to the mass of the object which means that an object having more mass has more inertia and an object having less mass will have less inertia.
\[\therefore {\text{ Inertia }} \propto {\text{ mass }}\]………(i)
Now, out of the given four options: football, thread, needle and refrigerator we know that thread will have the least mass. So, from the equation (i), we can say that thread will have the least inertia.

Thus, option (C) is the correct option.

Note:
Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion. The tendency of an object to resist changes in its state of motion varies with mass and a more massive object has more tendency to resist changes in its state of motion.