Aball is dropped from a cliff and falls a distance of 20 m to the ground. determine the velocity it hits the ground at and the time for the ball to fall. a. v = -10 m/s, t = 2 s b. v = 20 m/s, t = 4 s c. v = -20 m/s, t = 2 s d. v = 10 m/s, t = 2 s