SOLUTION: When it comes to word problems, as always, I have no idea of where to begin to arrive at the conclusion. Another question by the teacher, not in textbook... An object is prop

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: When it comes to word problems, as always, I have no idea of where to begin to arrive at the conclusion. Another question by the teacher, not in textbook... An object is prop      Log On


   

Question 84919This question is from textbook
: When it comes to word problems, as always, I have no idea of where to begin to arrive at the conclusion.
Another question by the teacher, not in textbook...
An object is propelled vertically upward from the top of a 112-foot building. The quadratic function s(t) = -16t2 + 176t + 112 models the ball’s height above the ground, s(t), in feet, t seconds after it was thrown. How many seconds does it take until the object finally hits the ground? Round to the nearest tenth of a second if necessary.
 This question is from textbook

Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
when the object hits the ground, s is 0 ... 0=-16t^2+176t+112 ... dividing by -16 gives 0=t^2-11-7

quadratic formula gives t=%2811+%2B-+sqrt%28%28-11%29%5E2-4%2A1%2A%28-7%29%29%29%2F%282%2A1%29 ... t=%2811+%2B-+sqrt%28149%29%29%2F2

t=11.6 and t=-0.6 ... negative value is not realistic