# Basic Special Relativity

## Homework Statement

A star is 27c*y away from the rest reference of earth. A rocket reaches star A from earth and according to clocks on it 12 hours have passed. How fast is the rocket traveling in earth's reference frame?

tpγ=t
Lp/γ=L

## The Attempt at a Solution

The problem is under the category of length contraction and time dilation so I assume these are the two equations I must use. However when trying to do the problem I only was given t and Lp, and yet there are three variables (tp, L, and v). Help ;-(

Related Introductory Physics Homework Help News on Phys.org
Can you calculate what time has passed wrt IRearth?
(I am assuming Earth is assumed to be an IR and the ship doesn't accelerate.)

yes, no acceleration.
I don't think I can calculate the time wrt IRearth..? I would need to know the velocity to do that so I knew the gamma factor correct?

vearth=dearth/tearth
tearth=dearth/vearth
plug and chug.

I don't know t_earth though? I only know it took 12 years from the spaceships frame..? oh... is Vearth 27c*y / 12 years...? i'm a noob X_X

but that's not REALLY the speed earth see's it moving is it? Because earth couldn't see the rocket traveling faster than C could it?

vearth=dearth/tearth
tearth=dearth/vearth
plug and chug.
tearthγ=t
or, tearth=t/γ
equate the tearth