: A 63.2-kg climber finds herself dangling over the edge of a cliff (see Fig. 5.7). Fortunately, she’s connected by a rope of negligible mass to a rock located 48.6 m from the edge of the cliff, and help is on the way. Unfortunately, it will be 36.5 s before help arrives, and the ice is frictionless. How massive must the rock be if she’s to be saved?

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?