SOLUTION: Solve: If an object is thrown upward with an initial velocity of 64 ft/sec, its height after t sec is given by h = 64t - 16t2. Find the number of seconds the object is in the ai

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Question 144914: Solve:
If an object is thrown upward with an initial velocity of 64 ft/sec, its height after t sec is given by h = 64t - 16t2. Find the number of seconds the object is in the air before it hits the ground.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
h+=+64t+-+16t%5E2
If you substitute t=0, you see that h=0
That is the time and the height when the object is
released.
What you want to find is another time when h=0,
and that will be the time when the object has come
back to earth, so
64t+-+16t%5E2+=+0
t%2864+-+16t%29+=+0
This equation is true if either of the factors, t, or
64+-+16t is zero
64+-+16t+=+0
t+=+4
So the object is in the air 4 sec before it hits the ground