Ageologist is observing the side of a mountain for evidence of erosion when a large rock begins to accelerate down the mountainside. using his knowledge of the laws of physics, what change should he conclude caused the rock to accelerate? a. when stationary the force of gravity on the rock was less, and when accelerating it was greater. b. when stationary there were no forces on the rock and when accelerating there were forces on it. c. when stationary there were equal forces on the top and bottom of the rock, but not on the left and right sides. d. when stationary the rock did not have a net force on it, and when accelerating it did.

To place a communications satellite into a geosynchronous orbit at an altitude of 22,240 mi above the surface of the earth, the satellite first is released from a space shuttle , which is in a circular orbit at an altitude of 185 mi, and then is propelled by an upper-stage booster to its final altitude. as the satellite passes through a, the booster's motor is fired to insert the satellite into an elliptic transfer orbit. the booster is again fired at b to insert the satellite into a geosynchronous orbit. knowing that the second firing increases the speed of the satellite by 4810ft/s, determine (a.) the speed of the satellite as it approaches b on the elliptic transfer orbit, (b.) the increase in speed resulting from the first firing at a.