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Physics Vector Question

  1. Sep 14, 2010 #1
    Physics Vector Question :)

    here is the question:

    The three vectors in Fig. 3-33 have magnitudes a = 2.97 m, b = 4.00 m, and c = 10.2 m and angle θ = 34.4°. What are (a) the x component and (b) the y component of a ; (c) the x component and (d) the y component of b; and (e) the x component and (f) the y component of c? If c= pa + qb, what are the values of (g) p and (h) q?

    2q9dtf6.gif

    my answers are
    a) 2.97 m
    b) 0 m
    c) 3.3 m
    d) 2.26 m
    e) -5.76
    f) 8.42 m
    g) ?
    h) ?

    I do not understand how to get p and q?
     
  2. jcsd
  3. Sep 14, 2010 #2
    Re: Physics Vector Question :)

    Look at the x and y components separately and solve the equations:
    p * x-component-of-a + q * x-component-of-b = x-component-of-c
    p * y-component-of-a + q * y-component-of-b = y-component-of-c
     
  4. Sep 14, 2010 #3
    Re: Physics Vector Question :)

    I did do that but I still don't understand how you are supposed to find 2 variables with 2 different letters.
     
  5. Sep 15, 2010 #4
    Re: Physics Vector Question :)

    using the first equation express p as a function of q and substitute that in the second equation.
    Example:
    (1) 2p+4q = 8
    (2) 3p+8q = 16
    from (1): 2p = 8-4q, so p = 4-2q
    substitute this in (2) to get:
    3(4-2q)+8q =16 and then solve that.
     
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