A waterfall had height of 1500 feet. A pebble is thrown upward from the top of the falls with an initial velocity of 12 feet per second.

Question

(continued) The height, h, of the pebble after t seconds is given by the equation h= -16t^2 + 12t +1500. How long after the pebble is thrown will it hit the ground? 

Answer 1

Set h(t) = 0 and solve the resulting quadratic equation for t.  Discard the negative solution.  The positive solution is the answer.