Question 1139714
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The object will hit the ground exactly and precisely at the time moment "t", when  h(t) = 0,  or, equivalently,


    {{{-16*t^2 + 48t + 64}}} = 0.


Simplify and solve for "t" :


    {{{t^2 - 3t -4}}} = 0

    (t-4)*(t+3) = 0.


The roots are t= 4  and  t= -3.  Only positive root  t= 4 is meaningful and provides the solution to the problem.


<U>ANSWER</U>.  In 4 seconds.
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