SOLUTION: a ball is thrown upward with an initial velocity of 96ft/s from a height 640ft. h = -16t^2 + 96t + 640. After how many seconds will the ball reach the ground?

Question 344469: a ball is thrown upward with an initial velocity of 96ft/s from a height 640ft. h = -16t^2 + 96t + 640. After how many seconds will the ball reach the ground?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
h = -16t^2 + 96t + 640
since h is height, set it to zero and solve for t:
0 = -16t^2 + 96t + 640
Dividing both sides by -16:
0 = t^2 - 6t - 40
0 = (t-10)(t+4)
.
t = {-4, 10}
we can toss out the negative solution leaving:
t = 10 seconds

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