Length (Lorentz) contraction
$$l_{r} = l\cdot \sqrt {1-\frac{v^{2}}{c^{2}}}$$
l_r - relative length
l - length of the object in its rest frame
v - speed (velocity)
c - speed of light
l - length of the object in its rest frame
v - speed (velocity)
c - speed of light
Find
It is known that:
= 