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If the temperature is constant, then the atmospheric pressure P (in pounds/square inch) varies with the altitude above sea level h in accordance with the law given below where p0 is the atmospheric pressure at sea level and k is a constant.

P = p0e-kh
If the atmospheric pressure is 14.9 lb/in2 at sea level and 12.6 lb/in2 at 4000 ft, find the atmospheric pressure at an altitude of 13,000 ft. (Round your answer to two decimal places.)

For this question I got 8.65 as my answer but for some reason I keep getting it wrong. Can someone please explain what I'm doing wrong.

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5 answers

  1. 12.6=14.9-k4000

    k=2.3/4000

    p=14.9-(2.3/4000)*13000

    p=7.43PSI recheck your calcs.

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  2. You forgot e in the calculations. I put in your number, it's not right. I'm sorry to be such a pain but I can't figure this out.

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  3. p=14.9* e^(-kh)
    12.6=14.9 * e^(-k4000) take ln of each side

    ln(12.6)= ln(14.9)-k4000
    .168=k*4000

    k=4.19E-5

    p=14.9 e^(-4.19E-5*13000)=14.9 e^(-.5447)
    p=8.65 PSI

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  4. Yeah, that's what I got too, but I keep getting the problem wrong. Don't worry about it though, I'm going to contact my professor and ask her what's going on. Thanks

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  5. The atmospheric pressure P in pounds per square inch (psi) is given by
    P = 14.7 e−0.21 a
    where a is the altitude above sea level (in miles). If a city has an atmospheric pressure of 11.39 psi, what is its altitude? (Recall that 1 mi = 5,280 ft. Round your answer to the nearest foot.)
    Incorrect: Your answer is incorrect. ft

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