102... Astronauts on a distant planet throw a rock straight upward and record its motion with a video camera. After digitizing their video, they are able to produce the graph of height, y, versus time, t, shown in FIGURE 2-46. (a) What is the acceleration of gravity on this planet? (b) What was the initial speed of the rock? y (m) 30 25 22 20 15 10 10 15 t(s) Ο 1 2 3 4 5 6 7 8 FIGURE 2-46 Problem 102