SOLUTION: Please help me solve this word problem: If an object is propelled upward from a height of 128 feet at an initial velocity of 112 feet per second, then its height h after t secon

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: Please help me solve this word problem: If an object is propelled upward from a height of 128 feet at an initial velocity of 112 feet per second, then its height h after t secon      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 132887: Please help me solve this word problem:
If an object is propelled upward from a height of 128 feet at an initial velocity of 112 feet per second, then its height h after t seconds is given by the equation h=-16t^2+112t+128. After how many seconds does the object hit the ground?
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Given :
h+=+-16t%5E2+%2B+112t+%2B+128
When the ball hits the ground, the value of h is 0. So
0+=+-16t%5E2+%2B+112t+%2B+128 divide through by 16
0+=+-t%5E2+%2B+7t+%2B+8+
factor the equation
0+=+%28-t+%2B+8%29%28t+%2B+1%29
So, either -t+8 = 0 or (t+1) =0
possible answers are t = 8 and t = -1
Since t cannot be 'minus time', only t = 8 makes sense.
Answer t = 8 seconds
Verify the answer by plugging 8 into the original equation, solve and verify the result is 0.