Calculator name  Summary 
Special relativity (Lorentz contraction) 
Calculates the length contraction of a body moving with some relative velocity with respect to the observer.

Special relativity (time dilation) 
Calculates the time dilation of a body moving for some time with some relative velocity with respect to the observer.

Special relativity (composition of velocities) 
Calculates the composition of two velocities.

Special relativity (massenergy) 
Calculates the massenergy of a body moving with some relative velocity with respect to the observer.
