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  1. #1
    Junior Member
    Joined
    Apr 2011
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    Navigation

    An airplane is flying in the direction of 148, with an airspeed of 875 kmh. Because of the wind, its groundspeed and direction are 800 kmh and 140, respectively. Find direction and speed of the wind.

    the airplane is heading South east.


    My set up:

    v1 : 875 < cos148, sin148 >
    v2 : 800 < cos140, sin140 >

    v= v1 + v2
    v= -1354.93, 980.91

    Resultant speed, ||V|| = 1672.73

    Direction : tan inverse ( 980.91/ -1354.93) = -35.90


    The answer they got is :

    N 21.4 E; 138.7 kmh.


    Am I doing this completely wrong?
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  2. #2
    Senior Member BAdhi's Avatar
    Joined
    Oct 2010
    From
    Gampaha, Sri Lanka
    Posts
    252
    Thanks
    6
    you've taken v1 and v2 in a wrong way. Instead of addition, you have to subtract the components. use V_{(w,e)}=V_{(w,p)}+V_{(p,e)}

    where w- wind, p-plane, e- earth and remember directions are important...
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