Question

why is it said that no object is at rest

Answer 1

According to the theory of relativity, it is said that an object is "at rest relative to" another. Two or more than twoobjects are said to be at rest, if its position with respect to each other isnot changing or moving with uniform velocity with respect to each other;rest and motion are relative terms. Hope it helps u. Please mark it as brainlist.

Answer 2

you can illustrate with this example
suppose you are travelling in a bus and with respect to you you are not moving but with respect to others you are going to your destination