Why do we think mercury has so many tremendous cliffs? a. they were probably carved in mercury's early history by running water. b. they are almost certainly volcanic in origin, carved by flowing lava. c. they represent one of the greatest mysteries in the solar system, as no one has suggested a reasonable hypothesis for their formation. d. they probably formed when a series of large impacts hit mercury one after the other. e. they were probably formed by tectonic stresses when the entire planet shrank as its core cooled.

Aball is thrown from the top of a building with an initial velocity of 21.9 m/s straight upward, at an initial height of 51.6 m above the ground. the ball just misses the edge of the roof on its way down, as shown in the figure. (a) determine the time needed for the ball to reach its maximum height. (b) determine the maximum height. (c) determine the time needed for the ball to return to the height from which it was thrown, and the velocity of the ball at that instant. (d) determine the time needed for the ball to reach the ground. (e) determine the velocity and position of the ball at t = 5.35 s.