Take the tour ×  Superman and Supergirl were playing catch. When
Superman is moving with a speed of 0.800c relative to Supergirl,
he threw a ball to Supergirl with a speed of 0.600c relative to
him.  a. What was the speed of the ball as measured by
Supergirl?  I tried to solve number 1. heres my approach. let s
be the supergirl frame of reference while s' be the frame of
reference by superman, heres my diagram  (<--)superman
(--->)ball     supergirl(stay)  so s' is going to the left, so
it has negative velocity (-0.8c). vx' is going to the right
(+0.6c) . now (vx) velocity of ball with respect to supergirl is
(-.13c)  using lorentz transformation, vx is negative, so it
means its going to the left and it will never reach supergirl.
so it appears that answer for letter a is, its impossible?
share|improve this question Why are you assuming that superman
is moving to the left while attempting to throw the ball to his
right? –  Willie Wong Jun 18 '12 at 14:29 i think im wrong, it
should be assumed that super