SOLUTION: A rocket is launched straight up into the air from the ground with an initial speed of 64 ft/s. The height of the rocket (in feet) is given by the equation: h = 16t squared + 64t,

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Question 80621: A rocket is launched straight up into the air from the ground with an initial speed of 64 ft/s. The height of the rocket (in feet) is given by the equation: h = 16t squared + 64t, where t is the time in seconds after launch. Find the time(s)when the rocket is at the ground level.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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A rocket is launched straight up into the air from the ground with an initial speed of 64 ft/s. The height of the rocket (in feet) is given by the equation: h = 16t squared + 64t, where t is the time in seconds after launch. Find the time(s)when the rocket is at the ground level.
:
I think the equation should be h = -16x^2 + 64t (gravity is pulling it down)
:
At ground level h = 0, so we have:
:
-16t^2 + 64t = 0
:
Factor out -16t and you have:
-16t(t - 4) = 0
:
t = 0 when it starts
and
t = +4 secs when it lands