SOLUTION: Suppose a model rocket is launched from a platform 2 ft above the ground with an initial upward velocity of 150 ft/s. How long will it take the rocket to hit the ground?
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Question 1083628: Suppose a model rocket is launched from a platform 2 ft above the ground with an initial upward velocity of 150 ft/s. How long will it take the rocket to hit the ground? Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! The equation is f(t)=-16t^2+150t+2
It hits the ground when f(t)=0
factor out a -2 and divide both sides by it.
8t^2-75t-1=0
t=(1/16)(75+/- sqrt (5625+32);sqrt 5657=75.21
use positive root only t=150.21/16=9.4 sec
Check by finding vertex t value which should be close (started +2 feet, so won't be exact) to half the entire time, since the vertex is the axis of symmetry.
t=-b/2a at vertex=-150/-32=4.7 sec.
Check again by graphing.
