Question 1153459
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<pre>

The object will hit the ground when


    -16*t^2 + 64 = 0   (i.e. when h(t) = 0 ).


It is the same as


    16t^2 = 64

    t^2   = 64/16

    t^2   = 4

    t     = {{{sqrt(4)}}} = 2.


<U>ANSWER</U>.  In 2 seconds.
</pre>

Solved.