Two Relativistic Moving Bodies

1. Oct 1, 2006

Gott_ist_tot

I am doing an extra problem from my textbook as review and I am stumped.

An Earth based observer sees to spaceships approaching Earth in the same direction. Spaceship A is travelling at 0.500c and Spaceship B is travelling at 0.800c. How fast is spaceship A traveleing as viewed by an observer on spaceship B?

I used a velocity transformation like:

(0.500c - 0.800c)/sqrt(1-[(0.5c)(0.8c)/(c^2)])

The book gets -0.500c.

I am finding it difficult to see that the Earth based observer and the spaceship moving at 0.800c observe that spaceship going the same speed.

2. Oct 1, 2006

3. Oct 1, 2006

Gott_ist_tot

Wow! It's always the simplest of mistakes. :yuck: Thanks a lot.