Two spaceships leave the earth in opposite directions, each with a speed of one-half the speed of light with respect to the earth. (a) what is the velocity of spaceship 1 relative to spaceship 2? (b) what is the velocity of spaceship 2 relative to spaceship 1?

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.