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Question 481908: Okay, this problem is algebra 2 but, I attempted to do some work on it but.... im stuck. It reads: the height of a diver jumping from a diving platform is about h= -16.1t^2 +11t+34.3
Where h is the height of the diver in feet above the water and t is the time measured in seconds, when diving from a platform about 34.3 feet above the water with an upward initial velocity of 11 ft/sec.
question: After how many seconds is the diver's height above the water 7 feet?
After how many seconds is the diver's height above water 36 feet?
*I set the whole thing up as an equation as I was taught in algebra 2 however, when I referred to my notes... we did not have 3 numbers on the right side of the equation... so, I attempted to solve it and I stopped at 27.3= -16.1t^2 +11t
Found 3 solutions by stanbon, solver91311, josmiceli:
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! It reads: the height of a diver jumping from a diving platform is about h= -16.1t^2 +11t+34.3
Where h is the height of the diver in feet above the water and t is the time measured in seconds, when diving from a platform about 34.3 feet above the water with an upward initial velocity of 11 ft/sec.
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question:
After how many seconds is the diver's height above the water 7 feet?
-16.1t^2+11t+34.3 = 7
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-16.1t^2+11t+27.3 = 0
Use the Quadratic Formula to get:
t = 1.6879 seconds
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After how many seconds is the diver's height above water 36 feet?
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-16.1t^2+11t+34.3 = 36
-16.1t^2 + 11t - 1.7 = 0
Use the Quadratic Formula to get:
t = 0.2362 seconds
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Cheers,
Stan H.
Answer by solver91311(24713)  (Show Source):
You can put this solution on YOUR website!
Is almost great way to start -- but you have a sign error.
\ =\ -16.1t^2\ +\ 11t\ +\ 34.3)
Add -34.3 to both sides:
Now, add 27.3 to both sides, leaving you with:
which you should recognize as a quadratic equation of the form:
where
 ,  , and 
and the solutions are:
In this case, since you are solving for time and you probably don't care what happened before the dive started at time = 0, you will discard any negative root.
You might find the arithmetic easier if you multiply the equation by 10 to get rid of the fractional coefficients. Using:
 ,  , and 
will give you the same results with simpler arithmetic.
The second problem is done in exactly the same way, with the exception that you will get two positive roots and both are valid. When the guy jumps he passes 36 feet on the way up (about 24 hundredths of a second into the dive) and then passes 36 feet again on the way back down (at about 0.45 sec).
John
My calculator said it, I believe it, that settles it
Answer by josmiceli(19441)  (Show Source):
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