Consider a keen little boy who is having a wagon race with a friend. he starts from rest and
then begins to accelerate to the left.
a) if the boy pulls with more force, will his wagon accelerate more or less than before?
b) if he pulls with the same force, but adds more books to his pile, will his wagon accelera
more or less than before?

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?