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Homework Help: Vector problem

  1. Sep 19, 2004 #1
    Vector problem plz help!!!!

    can any plz answer these 5 questions below
    i have a physics test coming up and i dont get those questions
    email me at david87chen@hotmail.com or teddyboi@gmail.com THX!!

    1. a plane has a speed of 300 km/h relative to the surround air. The wind is blowing from a direction of 25 degree west of south at 40 km/h. Calulate the speed of the plane with respect to the ground. Also find the direction in which the plane would move if the polot flew the plane in such a manner that it was always pointed towards the north according to the planes compass


    2. if the pilot of the plane in the above problem wish to fly directly towards the north, at what angle ( to the west of north) would the plane have to be pointed? Calculate the speed of the plane across the land in this case?


    3. assume that the pilot's intention had been to fly to a community 600 km directly norht of the starting point. How long wold the pilot expect the trip to last? use the plane's speed with respect to the air.


    4. considering the plane's actual path, how far from its intended destination is the plane after the time in quesiton #3? Begin by finding the displacement along the vector v using your value for the velocity with respect to the ground, from question #1


    5. using the velocity with respect to the ground from question #2 calculate how long it actually takes the plane to fly directly to the community that is 600 km to the north.


    thats all plz email me at david87chen@hotmail.com or teddyboi@gmail.com
  2. jcsd
  3. Sep 19, 2004 #2
    All of these involve vector work (as you know). If you understand how to use vectors, you shouldn't have a problem, so I'm assuming you don't understand how to use vectors. You can draw vectors (visual representations of magnitude and direction) for many things: displacement, velocity, force, momentum...any vector value. Draw the velocity vectors for each of the problems above, and analyse them vectorally (using trig or x/y components). I think you should be able to solve these problems from there. I think for the first question you assume the plane is flying in the same direction as the wind.
  4. Sep 19, 2004 #3
    Do you expect a numerical answer? If so you're missing a piece of information about the direction of the airplane. If your question is written correctly then all of your answers for the first part of the question will be functions of the planes heading. Show what you've done thus far so you can get the help you need.
  5. Sep 19, 2004 #4
    &\vec{v_{pa}}=relative\ velocity\ of\ plane\ to\ air\\
    &\vec{v_a}=relative\ velocity\ of\ air\ to\ ground\\
    &\vec{v_p}=relative\ velocity\ of\ plane\ to\ ground\\
    &\vec{v_{pa}}=300(cos\ \theta\vec{i}+sin\ \theta\vec{j})\\
    &\vec{v_a}=40(cos\ 65^0\vec{i}+sin\ 65^0\vec{j})\\
    &\vec{v_p}=V\vec{j}\ with\ V>0\\
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