Relativity question reworded...?

Question

In relativity, as speeds increase for something time slows down for that something to an outside viewer. Something needs energy to accelerate to any speed. Is there an equation showing the relationship between energy, and the amount time changed to the outside viewer, in this instance of relativity?

Answer 1

Here's the formula for time dilation:

http://www.drphysics.com/syllabus/time/time.html

and more detail here:
http://en.wikipedia.org/wiki/Time_dilation#Overview

Answer 2

Use E=mc^2 and 1/sqrt[1-v^2/c^2].