# Relativistic Rocket: Finding the change in velocities in different reference frames

1. Feb 9, 2012

### Hebrew21

1. The problem statement, all variables and given/known data
I a little lost on how to use the relativistic velocity addition formula to determine the increase in speed "v" over a short time interval in the Earths frame of reference, for a rocket having left earth at rest and traveling through space accelerating at constant acc. of 9.81 m/s^2. In the rockets instantaneous frame of reference, the increase in speed is (9.81m/s^2)*Δt where Δt is the proper time interval. The equation must be modified to determine a speed increase Δv over a short interval of time from the Earth frame of reference. I guess the question I have is if I can use this formula to solve for the change in velocity over a small interval of time, for a different reference frame?

2. Relevant equations

v=u+v'/ sqrt(1+v'u/c^2)

3. The attempt at a solution
Here's what I have so far, not sure if its close:

Δv=9.81*Δt/sqrt(1+9.81*Δt/c^2)

Last edited by a moderator: Feb 9, 2012
2. Feb 9, 2012

### vela

Staff Emeritus
Re: Relativistic Rocket: Finding the change in velocities in different reference fram

You should review the velocity-addition formula. Identify what v, u, and v' stand for as it relates to this particular problem, and then try again.