Question

What is absolute rest?

Answer 1

Hint: Absolute rest is something you can take as fixed and non-variable things. It is only possible when the net force working on it is zero, in other words, the resultant force of superposition of other particles from all directions is taken as zero.

Complete step by step answer:
For example: Consider the Kelvin scale; it's called an absolute scale for temperature in our universe because nothing can achieve zero Kelvin or less then it.

Absolute rest refers to a special inertial frame, which is at rest, and with respect to which all other motion should be measured

Similarly, in classical mechanics, to study the motion we have to define the object with the same frame of reference which will be comfortable while doing analysis. But nothing is at rest if we change the frame of reference, absolute rest must become the imaginary thing. But to understand the concept, consider absolute rest for example you throw a ball on the wall, with respect to the wall, the ball is moving. So, the wall can be considered as at the absolute rest and the ball as absolute motion.

Similarly, while travelling in the train, consider the ball in your pocket. To you the ball in your pocket is at absolute rest and you neglect small body movement/vibration of the train. But the ball will be in absolute motion for a person outside the train.

Additional information:
Given an inertial frame of reference, Newton’s law of motion states that an object is at rest at rest, while the motion of a moving object will remain unchanged until and unless acted upon by an external force.
When an object is at rest it means the velocity and acceleration are zero, so as per the theory of relativity, an object is either at rest or in motion relative to other moving objects.

Note: Students must know that a body is said to be at absolute rest, that is, the state of an object is stationary relative to a particular frame of reference or another object.
When the position of the body does not change with respect to its surroundings or with respect to the time it is said to rest. According to the theory of relativity, it is said that an object is 'at rest relative to' another.