Un niño lanza piedritas a la ventana de su amigo, que está a 4.5m de altura y a 5m de distancia horizontal desde la pared. Si quiere que las piedritas toquen la ventana sólamente con una velocidad horizontal (vy = 0), qué velocidad tendrían las piedritas al tocar la ventana?

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?