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AQA M1 help needed - finding a vector given bearing and distance Watch

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    What the title says. Trying to self teach M1 and with 2 weeks to go, its going to be something of a crash course. Currently stuck, and the Heinemenn book doesn't do a great job of explaining how to find a vector given distance and bearing. Any help would be appreciated.
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    Do you have an example ?
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    You can do trig.
    You can figure out the angle, and then d sin theta and d cos theta to find the other sides

    _Tyrion
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    (Original post by metrize)
    You can do trig.
    You can figure out the angle, and then d sin theta and d cos theta to find the other sides

    _Tyrion
    Yeah, this is what I do, but my problem is drawing the triangle. I'm OK with drawing the first line (the bearing and the distance one) but then theres loads of options for drawing a right angled triangle. I end up just guessing, and I'm correct about 50% of the time.

    If you don't know what I mean, I can take a picture? Anyone?
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    (Original post by _Tyrion)
    Yeah, this is what I do, but my problem is drawing the triangle. I'm OK with drawing the first line (the bearing and the distance one) but then theres loads of options for drawing a right angled triangle. I end up just guessing, and I'm correct about 50% of the time.

    If you don't know what I mean, I can take a picture? Anyone?
    Send me the question
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    (Original post by metrize)
    Send me the question
    A ball is thrown so that its initial velocity is 8ms^-1 at an angle of 50 degrees above the horizontal. The united vectors i and j are horizontal and vertical, respectively. Express the initial velocity of the ball in terms of the unit vectors i and j.

    What I did is start off drawing an x and y axis, then drew a line at 50 degrees with length 8. How do I finish off the triangle after this? I can either draw a horizontal line that touches the y axis to complete the triangle or a vertical line that touches the x axis to complete the triangle.

    My final answer was 6.13i + 5 14j.
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    (Original post by _Tyrion)
    A ball is thrown so that its initial velocity is 8ms^-1 at an angle of 50 degrees above the horizontal. The united vectors i and j are horizontal and vertical, respectively. Express the initial velocity of the ball in terms of the unit vectors i and j.

    What I did is start off drawing an x and y axis, then drew a line at 50 degrees with length 8. How do I finish off the triangle after this? I can either draw a horizontal line that touches the y axis to complete the triangle or a vertical line that touches the x axis to complete the triangle.

    My final answer was 6.13i + 5 14j.
    I and J always form a right angle
    I got j=6.13 and i=5.14

    See below
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    (Original post by metrize)
    I and J always form a right angle
    I got j=6.13 and i=5.14

    See below
    Why is the angle 50 degrees? Howcome it isn't 40 degrees? Because the angle between the line which is 5ms^-1 and the y axis is 50 degrees, so the angle in the triangle is 90-50=40?
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    (Original post by _Tyrion)
    Why is the angle 50 degrees? Howcome it isn't 40 degrees? Because the angle between the line which is 5ms^-1 and the y axis is 50 degrees, so the angle in the triangle is 90-50=40?
    Its 50 from the horizontal, so since i is horizontal its 50 from i
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    (Original post by metrize)
    Its 50 from the horizontal, so since i is horizontal its 50 from i
    Aah right, thanks. If they hadn't specified that it is 50 degrees from the horizontal and instead just said it was on a bearing of 050 degrees, would it have been how I said it or not?
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    (Original post by _Tyrion)
    Aah right, thanks. If they hadn't specified that it is 50 degrees from the horizontal and instead just said it was on a bearing of 050 degrees, would it have been how I said it or not?
    Yep, then you would have been right
 
 
 
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