Question

Define the state of rest and the state of motion of an object.

Answer 1

Hint : To answer this question, we have to analyse the motion of a given object with reference to a particular frame of reference. The state of the object can be different relative to different reference frames.

Complete step by step answer
The state of rest and the state of motion of an object are the relative terms. They are not defined in absolute terms. So first a frame of reference has to be chosen in order to define the state of the object. For example, when we are standing on the ground and observe the state of other objects, then the ground becomes our frame of reference. On the other hand, if we are observing the state of an object while sitting in a moving car, then the moving car becomes our frame of reference.
The state of rest of an object is defined as the state when the position of the object does not change with time relative to the frame of reference. For instance, with the ground as the frame of reference, the trees, buildings, pillars etc. are in the state of rest
The state of motion of an object is defined as the state when the position of the object changes with time relative to the frame of reference. If we take the ground as our frame of reference, then all the moving vehicles are in the state of motion.
The state of an object is not fixed. It may vary depending upon the choice of reference frame. For example, a moving car appears to be in the state of motion in the frame of ground. But if a train moving with the same speed as that of the car is selected as the frame of reference, then the car appears to be in the state of rest.

Note
We stated above that the state of an object depends on the choice of reference frame. But there is an exception to this statement. The state of light is not dependent on any reference frame. It always appears to be moving with the same speed, from whichever frame it is observed.