Question

An observer is moving with a velocity of 0.95c in a direction perpendicular to a rod of length L the observer will measure the length of the rod to be

Answer 1

Theory of Relativity :  
    Length contraction due to relative speed of the observer wrt the object.

Length measured by moving observer = L
Length measured in the inertial rest frame of the object = L₀
velocity of the object = v = 0.95 c
speed of light = c

Lorentz factor = $\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$

L = $=\frac{L_0}{Lorentz \: factor}=L_0 \sqrt{1-\frac{v^2}{c^2}}$
L = $L= L_0 *\sqrt{1-0.95^2}=0.0975 \: L_0$

The length becomes only 9.75% of its rest length.

Answer 2

it is from theory of relativity