Equations of special relativity
An object of rest mass mo and length Lo, moves with velocity v relative to a stationary frame of reference.
The following equations give the mass m, length L and time t as measured from the frame of reference.
m = mo/[1-v2/c2]½
The faster the object moves relative to the observer the greater is its mass
L = Lo[1-v2/c2]½
The faster the object moves relative to the observer the smaller is its length
t = to/[1-v2/c2]½
The faster the object moves relative to the observer the slower time passes