List of top Physics Questions on Relativity asked in BHU PET

A clock keeps correct time. With what speed should it be moved relative to an observer so that it may seem to lose 20 sec in 100 sec?
With what velocity should an electron move so that its kinetic energy equals its rest mass energy?
If the volume of a cube of side \( L_0 \) is \( L_0^3 \) as observed by an observer at rest relative to it, the volume as observed from a reference frame moving with uniform velocity \( 0.8c \) in a direction parallel to an edge of the cube will be: