Word Problem and Equations

Question

A waterfall has a height of 1700 feet. A pebble is thrown upward from the top of the falls with an initial velocity of 12 ft per second. The height of the pebble h in feet after t seconds is given by the equation h=-16ft²+12t+1700. How long after pebble is thrown will it hit the ground?

Answer 1

It hits the ground at h=0. so -16t² + t + 1700 =0 . use quadratic formula to solve

t = -12 ± √(12 - 4(-16)(1700)) ⁄ -32

do the math and you get t = (-12±330)/-32

time has to be positive here so its (-12-330)/-32 = 10.7 sec