Question 136113
Given: {{{h = -16t^2 + 112t + 128}}}

When does it hit the ground? Means, when does h = 0

{{{0 = -16t^2 + 112t + 128}}}
{{{0 = -t^2 + 7t + 8}}}
{{{ 0 = t^2 -7t -8}}}
{{{ 0 = (t-8)(t+1)}}}
t = 8, -1

Since t cann hit the ground a second before you throw it, the only reasonable answer is 8 seconds.

Check your answer by using 8 for t and finding h