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Does the plane strike the ground?

  • Thread starter Drub
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1. Homework Statement
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?


upload_2015-8-29_22-13-0.png

2. Homework Equations
upload_2015-8-29_22-13-11.png


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.
 

andrewkirk

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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
 
7
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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.'

EDIT:
However, i am still unsure where to take this problem with the information listed above.
 
Last edited:

billy_joule

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

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.
Can you draw a diagram of this triangle?
 
7
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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.
 

CWatters

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I solved for the adjacent and then did delta x= vi*t+1/2(a*t^2).
That equation is somewhat overkill for this problem. Easier to use..

velocity = distance/time
or
time = distance/velocity.
 

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