Question 145012
If an object is thrown upward with an initial velocity of 64ft/sec, its height after t sec is given by h=64t-16t^2. Find the number of seconds the object is in the air before it hits the ground. 
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h(t) = 64t-16t^2
Height is zero when the object hits the ground.
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64t - 16t^2 = 0
-16t(-4 + t) = 0
t = 0 or to = 4 seconds
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The object is in the air 4 seconds.
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Cheers,
Stan H.