The length of a rod is exactly 1m when measured at rest. What will be its length when it moves at a speed of

(a) 3 × 105 m s–1


(b) 3 × 106 m s–1 and


(c) 3 × 107 m s–1?


Whenever the object moves with the speed comparable to the speed of light, the length of the object contracts. So, let us consider the following cases when the speed of rod is comparable to the speed of light.

(a) length of the rod= 1m


Speed of the rod= 3 × 105 m s–1


Using the relativistic relation of length contraction



The length observed will be 0.99999995m


(b) length = 1m


Speed= 3 × 106 m s–1



(c) length= 1m


Speed = 3 × 107 m s–1



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