Determine the speed of the shuttle craft

[fredrick08]

Homework Statement

A spaceship moves away from the Earth at a speed v, and fires a shuttle craft in the forward direction at a speed v relative to the ship. The pilot of the shuttle craft forward launches a probe at a speed v relative to the shuttle craft. Detrmine:

a) the speed of the shuttle craft relative to Earth
b) the speed of the probe relative to Earth

The Attempt at a Solution

Im just completely confused with this question, do i have to use Lorentz transformations?? but if so, how do i compute an answer?? please can someone help, completely lost with this one.

 

[CompuChip]

You can just use the velocity addition formula I suppose.
Apparently someone else is working on the exact same question in this thread.

 

[fredrick08]

ok for part a, i can use the LT to get u=2v/(1+v^2/c^2) but how do i do b.??

i can use u'=u from part a, but I am sure if this is what i have to do

 

[tyco05]

I think you are making it harder for yourself than it actually is.

Just use simple velocity addition.

 

[HallsofIvy]

I think you are making it harder for yourself than it actually is.

Just use simple velocity addition.

And what do YOU mean by "simple velocity addition"? It looks to me like that is what he is trying to do!


Fredrick08, yes, you use the same formula again, this time with one of the velocities given by 2v/(1+v^2/c^2) and the other by v.