8. A student is throwing rocks off a bridge straight down into a river below. If he throws a rock with an initial speed of 10.0 m/s and it hits the water with a speed of 31 m/s, how high is the bridge? a. 23 m b. 54 m c. 44 m d. 43 m 9. A water balloon is thrown straight down from a window 8.0 m above the ground. If it is thrown with an initial speed of 6.0 m/s, what is the speed with which it hits the ground? a. 13 m b. 14 m c. 11m d. 12 m