Question 109037This question is from textbook university of Phoenix Elementary and Intermediate Algebra
: If the balloonist of Exercise 83 throws his sandbag downward from an altitude of 128 feet with an initial velocity of 32 feet per second, then its altitude after t seconds is given by the formula h=-16t^2-32t+128. How long does it take for the sandbag to reach the earth?
I'm really struggling with this one, just wondering if anyone would be kind enough to help. Thanks so much!!!
This question is from textbook university of Phoenix Elementary and Intermediate Algebra
Found 2 solutions by stanbon, ankor@dixie-net.com:
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! If the balloonist of Exercise 83 throws his sandbag downward from an altitude of 128 feet with an initial velocity of 32 feet per second, then its altitude after t seconds is given by the formula h=-16t^2-32t+128. How long does it take for the sandbag to reach the earth?
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It's height is zero when it hits the ground so let h=0
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-16t^2-32t+128 = 0
t^2+2t-8 = 0
(t+4)(t-2)=0
Positive answer:
t = 2 seconds
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Cheers,
Stan H.
Answer by ankor@dixie-net.com(22740)  (Show Source):
You can put this solution on YOUR website! If the balloonist of Exercise 83 throws his sandbag downward from an altitude of 128 feet with an initial velocity of 32 feet per second, then its altitude after t seconds is given by the formula h=-16t^2-32t+128. How long does it take for the sandbag to reach the earth?
:
The altitude of the earth is 0, therefore h = 0, find t when h = 0
:
-16t^2 - 32t + 128 = 0
:
Simplify, divide equation by -16, This changes the signs, makes it easy to factor
+t^2 + 2t - 8 = 0
:
Factors to:
(t + 4)(t - 2) = 0
:
t = -4
and
t = +2, only the positive solution is wanted here
:
2 seconds to travel the 128ft downward
:
Since he is throwing it downward, it's velocity is combined with the force of gravity.
:
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