Posted by **Amy** on Thursday, April 18, 2013 at 8:02pm.

An object is launched upward from the ground with an initial vertical velocity of 40 feet per second. After how many seconds does the object reach a height of 25 feet? I need to use the vertical motion model. Here is my work so far.

h = -17t^2 + 40t + 25

- Algebra -
**Amy**, Thursday, April 18, 2013 at 8:03pm
I meant -16t^2

- Algebra -
**Reiny**, Thursday, April 18, 2013 at 8:44pm
your opening function should be

h = -16t^2 + 40t

h is supposed to have a value of 25

25 = -16t^2 + 40t

16t^2 - 40t + 25 = 0 , looks like a perfect square

(4t - 5)^2 = 0

4t = 5

t = 5/4

it will take 5/4 seconds

I don't know what "vertical motion model" means, never heard that term

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