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Does the plane strike the ground?

  1. Aug 29, 2015 #1
    1. The problem statement, all variables and given/known data
    A pilot flies horizontally at 1300 km/h, at height h = 76 m above initially level ground. However, at time t = 0, the pilot begins to fly over ground sloping upward at angle θ = 7.5° (see the figure). If the pilot does not change the airplane's heading, at what time t does the plane strike the ground?

    2. Relevant equations

    3. The attempt at a solution
    Second question today, been taking chunks at my homework all throughout the day!

    So i know the Xi is 76 m. I know that the Vi is 36.11 m/s once i convert from kilometers. I know my t=0 and that since the plane is falling, my a = 9.8 m/s^2. im not sure what the angle 7.5 does to the problem however. That is where I am stuck.
  2. jcsd
  3. Aug 29, 2015 #2


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    Why do you say the plane is falling? The question says it is flying horizontally.

    There is no need to bring gravity into this question. It's just trigonometry. You have a right triangle with the two non-hypotenuse sides 76m and x metres where x is the distance flown between t=0 and the crash, and the angle is 7.5 degrees. So you can work out x and then work out t from that using the plane's speed.

    By the way, your calc of speed in m/s is wrong. 10m/s is 36 km/h. So 1300 km/h is going to be an awful lot more than 36.11 m/s
  4. Aug 29, 2015 #3
    Thank you for your response!
    It seems i screwed up a basic conversion, what I meant to say that it was 361.11 m/s.'

    However, i am still unsure where to take this problem with the information listed above.
    Last edited: Aug 29, 2015
  5. Aug 30, 2015 #4


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    Was there something about the following you didn't understand?

    Can you draw a diagram of this triangle?
  6. Aug 31, 2015 #5
    I worked through the problem again and understood what you were saying earlier :) I solved for the adjacent and then did delta x= vi*t+1/2(a*t^2). ended up with 1.60 s as the final answer and was right. Thank you :3.
  7. Aug 31, 2015 #6


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    That equation is somewhat overkill for this problem. Easier to use..

    velocity = distance/time
    time = distance/velocity.
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