An object may be regarded to be at rest or in motion depending on the frame of reference chosen to view the object. Because of length contraction it would mean that the same rod may have two different lengths depending on the state of the observer. Is this true?

Let the speed of rod is v, the length is given by



Where, l0 = Length of rod at rest


` c = Speed of light >> v


Now assume that the observer and the rod are moving with the speed v in same direction. The length of the rod is given by,




Thus, it is true that an object may be regarded to be at rest or in motion depending on the frame of reference chosen to view the object.


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