A model rocket is launched from the top of a cliff 144 feet above sea level. The function
s(t) = -16t^2+128t+144
describes the rocket's height above the water, s(t), in feet, t seconds after the rocket is launched. How long will it take for the rocket to his the water?
s(t) = -16t^2+128t+144
describes the rocket's height above the water, s(t), in feet, t seconds after the rocket is launched. How long will it take for the rocket to his the water?
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Set the equation equal to zero and solve for t
-16t^2 + 128t + 144 = 0
Divide by a common factor of -16
t^2 - 8t - 9 = 0
Factor
(t - 9)(t + 1) = 0
t = 9, t = -1
There's no such thing as negative time so it takes 9 seconds.
-16t^2 + 128t + 144 = 0
Divide by a common factor of -16
t^2 - 8t - 9 = 0
Factor
(t - 9)(t + 1) = 0
t = 9, t = -1
There's no such thing as negative time so it takes 9 seconds.
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16t^2 = 128t so t = 128/16 = 8 sec going up
128 * 8 = 1024 ft up
1024 + 144 = 1168 ft down
s = 1168 = Vo + 16t^2 (Vo = 0)
t^2 = 1168/16
total time = 8 + sqrt(1168/16)
128 * 8 = 1024 ft up
1024 + 144 = 1168 ft down
s = 1168 = Vo + 16t^2 (Vo = 0)
t^2 = 1168/16
total time = 8 + sqrt(1168/16)