SOLUTION: A stone is thrown into a well with an intial speed of 8 feet per second. The well is 80 feet deep. How long will it take for the stone to hit the bottom of the well? Use the equ

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A stone is thrown into a well with an intial speed of 8 feet per second. The well is 80 feet deep. How long will it take for the stone to hit the bottom of the well? Use the equ      Log On


   

Question 153474: A stone is thrown into a well with an intial speed of 8 feet per second. The well is 80 feet deep. How long will it take for the stone to hit the bottom of the well? Use the equation d=vt+16t^2. where d=depth of the well, v= initial speed, and time
choices:
1) 2
2) 5/2
3) 2 or 5/2
4) none of these
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A stone is thrown into a well with an intial speed of 8 feet per second. The well is 80 feet deep. How long will it take for the stone to hit the bottom of the well? Use the equation d=vt+16t^2. where d=depth of the well, v= initial speed, and time
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EQUATION:
d(t) = vt + 16t^2
80 = 8t + 16t^2
10 = t + 2t^2
2t^2 + t - 10 = 0
2t^2 + 5t - 4t - 10 = 0
t(2t+5) -2(2t+5) = 0
(2t+5)(t-2) = 0
Positive solution:
t = 2 seconds
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Cheers,
Stan H.
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choices:
1) 2
2) 5/2
3) 2 or 5/2
4) none of these