Suppose a spaceship A and a spaceship B are moving towards each another. Spaceship A fires a missile at spaceship B. The speed of the missile, relative to spaceship A, is . The speed of the missile, relative to the spaceship B, is . What is the relative velocity of the two spaceships?
Two planets are on a collision course, heading directly toward each other at a speed of . A spaceship sent from one of the planets approaches the other planet at a speed of as measured in the reference frame of the other planet. What is the speed of the ship relative to its planet of origin?