If a toy rocket is launced vertically upward from ground level with an inital velocity of 128 feet per second, then its high h, after t seconds is given by the equation h (t) = - 9t^2 + 81 round to the nearest foot when does the ball hit the ground?

Question

Mathematics

Brenton Day

30 July, 13:05

If a toy rocket is launced vertically upward from ground level with an inital velocity of 128 feet per second, then its high h, after t seconds is given by the equation h (t) = - 9t^2 + 81 round to the nearest foot when does the ball hit the ground?

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Answers (1)

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Cash Cain · Answer 1

The toy rocket hits the ground when h (t) = 0.

So, h (t) = 0 = - 9t^2 + 81.

Solving the equation,

-9t^2 = - 81

Dividing by - 9

t^2 = 9

Taking the square root.

t = 3

The answer is 3 seconds.