Question

The length of a rod seems shorter to an observer when it moves in a specific direction. What change would he observe when the direction of rod changes by 180^o?

(a) The rod becomes even smaller

(b) The length of the rod increases

(c) The length of the rod remains the same

(d) The rod has the length equal to its proper length

The question was asked by my school teacher while I was bunking the class.

My question is from Lorentz Transformation Equations topic in portion Ultrasonics & Relativity of Engineering Physics I

Answer 1

Right option is (c) The length of the rod remains the same

The explanation: As we know, by Lorentz contraction, l = l0\(\sqrt{1-\frac{v^2}{c^2}}\).

Thus, as it deals with the square of velocity, v, there is no effect on the length of the rod by changing the direction of the rod from v to -v.