+16 Jorge is kicking a ball straight up into the air. The height of the ball is described by the equation h=-16t^2+20t, where h is the height of the ball and t is the time in seconds. How long will it take the ball to hit the ground?
+37146 When the ball hits the ground, it's height is 0
0 = -16t^2 + 20 t
divide through by 4
-4t^2 + 5t = 0 t(-4t+5) = 0 so t = 0 (when he kicks it) and 5/4 sec (when it comes back down and hits the ground)
