Suppose you are on a rooftop and you throw a ball downward to the ground with an initial speed v0. You then throw an identical ball upward with the same initial speed v0. After rising, this ball also falls to the ground. When each ball strikes the ground, which ball has the larger speed

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?