Bob and Bob Jr. stand at open doorways at opposite ends of an airplane hangar 25 m long. Anna owns a spaceship, 40 m long as it sits on the runway. Anna takes off in her spaceship, then swoops through the hangar at constant velocity. At precisely time zero on both Bob's clock and Anna's, Bob sees Anna at the front of her spaceship reach his doorway. At time zero on his clock, Bob Jr. sees the tail of Anna's spaceship at his doorway.
A) How fast is Anna's spaceship moving?
v/c = 0.781
L = Lo / Yv
--> 25 = 40 (square root) 1 - (v/c)^2
But how do you solve for v? I tried subtracting 25 and squaring it to get rid of the square root. But I just don't know how to get to v = 0.781 c
Thank you for any help