SOLUTION: the height h of a toy rocket t seconds after launching is determined by the formula h= -16t^2 + 112t a)find the height of the rocket 2.5 seconds after launching b) afer how many

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Question 192759: the height h of a toy rocket t seconds after launching is determined by the formula h= -16t^2 + 112t
a)find the height of the rocket 2.5 seconds after launching
b) afer how many seconds is the rocket 196 feet above the ground?
c) when will the rocket hit the ground?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
the height h of a toy rocket t seconds after launching is determined by the formula h= -16t^2 + 112t
a)find the height of the rocket 2.5 seconds after launching
h(2.5) = -16(2.5)^2 + 112(2.5) = 180 ft.
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b) afer how many seconds is the rocket 196 feet above the ground?
-16t^2 + 112t = 196
-16t^2 + 112t - 196 = 0
t^2 - 7t + 12.25 = 0
t = [7 +- sqrt(49 - 4*1*+12.25)]/2
t = [7 +- sqrt(49 - 49)]/2
t = [7 +- sqrt(0)]/2
Positive solution:
t = 7/2 = 3.5 seconds
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c) when will the rocket hit the ground?
-16t^2 + 112t = 0
-16t(t - 7) = 0
t = 0 (means it starts on the ground)
t = 7 sec (means it ends up on the ground in 7 seconds)
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Cheers,
Stan H.