A rock is thrown upward from the height of 5 ft with an initial velocity of 50 ft per second. The height h(in feet) of the rock at time t seconds is h(t)=-16t^2+50t+5. When will the rock reach a height of 8 ft?
h(t) = 8 ft
8 = -16t^2 + 50t+5
-16t^2 + 50t -3 = 0 Use quadrtatic formula a = -16 b = 50 c = -3
you will get two values for 't' at 8 ft one is going up one is coming back down
obviously the smaller value will be the first time the rock reaches 8ft ...on the way up