When your spaceship is waiting to be launched,
it has a rest
mass of m_{0}. When it’s in flight,
it has a mass m, also known as its relativistic
mass or moving mass. The
relationship of these two masses is shown in this equation:
where and v is
the speed of the spaceship.
Note that is always greater than 1, so m is
always greater than m_{0}.
Try this!
Enter two values into the calculator—a fraction of the speed
of light (from 0 to 0.999 999 999) and the rest mass of an object
(your own mass, perhaps)—and
the Moving Mass will tell you how massive the object
would be at that speed.
If you don't know how many kilograms your mass is, you can divide
your weight in pounds by 2.2 to find out. Mass and weight are different
quantities, but they're directly proportional, so we can convert
from one to the other. At the surface of Earth, an object with
the mass of 1 kilogram weighs 2.2 pounds.
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