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Homework Help: A question regarding kinematics

  1. May 17, 2008 #1
    1. The problem statement, all variables and given/known data
    A small plane flies a heading of 200km/h [W]. The wind speed is 50.0km/h [N]
    a) Determine the resultant groundspeed and direction of the plane
    b) What heading would the plane need to take to travel due west, and what would his ground speed be?

    2. Relevant equations
    r^2=a^2 + b^2

    3. The attempt at a solution
    So for a):
    r^2 = (200)^2 + (50.0)^2
    r = 206 km/h
    tan(theta) = 50/200
    (theta) = 14
    Therefore, the resultant groundspeed and direction is 206 km/h W14N.

    But, for b), I'm not so sure what the difference is between what I just did for a) compared to the question b). I'm sorry am I missing anything?
  2. jcsd
  3. May 17, 2008 #2
    for part b, you want your resultant vector to point west,
    but for part a, your resultant vectors point at 14 degrees

    draw a vector diagram (with resultant ground vector speed of unknown mag pointing west)

    and plane air speed (pointing little south at x degrees) and air speed pointing north

    you are trying to find that x
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