SOLUTION: An object is thrown downward with an initial velocity of 8 feet per second. The relationship between the distance s it travels and time t is given by s=8t+16t^2. How long does it t

Algebra ->  Equations -> SOLUTION: An object is thrown downward with an initial velocity of 8 feet per second. The relationship between the distance s it travels and time t is given by s=8t+16t^2. How long does it t      Log On


   

Question 1175489: An object is thrown downward with an initial velocity of 8 feet per second. The relationship between the distance s it travels and time t is given by s=8t+16t^2. How long does it take the object to fall 80 feet?
Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
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To answer this question, solve an equation


    16t^2 + 8t = 80  feet.


Cancel factor 8 in both sides


    2t^2 + t - 10 = 0


    t%5B1%2C2%5D = %28-1+%2B-+sqrt%28%28-1%29%5E2+%2B+4%2A2%2A10%29%29%2F%282%2A2%29 = %28-1+%2B-+sqrt%281%2B80%29%29%2F4 = %28-1+%2B-+sqrt%2881%29%29%2F4 = %28-1+%2B-+9%29%2F4.


Take the positive root  t = %28-1+%2B+9%29%2F4 = 2 seconds.      ANSWER

Solved.