Two students noted that the acceleration of a car was -40 km/s^2. The first student said, “That can’t be right. You can’t have a negative acceleration.” The second student said, “That can’t be right. You can’t have s^2.” What would you say to each student to help them better understand how acceleration is described?

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? 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 marias voyage take according to samir?