physics
posted by beth .
A box is cubical with sides of proper lengths L1=L2=L3=2.0m when viewed in it own rest frame. If this block moves parallel to one of its edges with a speed of 0.80c past an observer,
(a) What shape does it appear to have to this observer, and
(b) What is the length of each side as measured by the observer?
The edges parallel to the direction the box travels will have shortened by a factor
1/gamma = sqrt[1v^2/c^2] = 0.6

It's correct