Question 343420: (Modeling) Airplane Landing Speed
To determine the appropriate landing speed of a small airplane, the formula
D= .1s^2 - 3s + 22
is used, where s is the intitial landing speed in feet per second and D is the length of the runway in feet. If the landing speed is too fast, the pilot may run out of runway; if the speed is too slow, the plane may stall. If the runway is 800 ft long, what is the appropriate landing speed? Round to the nearest tenth.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Airplane Landing Speed
To determine the appropriate landing speed of a small airplane, the formula
D= .1s^2 - 3s + 22
is used, where s is the intitial landing speed in feet per second and D is the length of the runway in feet. If the landing speed is too fast, the pilot may run out of runway; if the speed is too slow, the plane may stall. If the runway is 800 ft long, what is the appropriate landing speed? Round to the nearest tenth.
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Solve:::
0.1s^2 - 3s + 22 = 800
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Rearrange:
0.1s^2 - 3s - 778 = 0
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Quadratic Formula:
s = [3 +- sqrt(9 - 4*0.1*-778)]/(0.2)
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s = [3 +- sqrt(9 + 320.2)]/0.2
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Positive Solution:
s = [21.14]/0.2
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s = 105.71 mph
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Note: My calculator says the answer is 104.47 mph
Check it out.
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Cheers,
Stan H.
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