Page 2 of 2 FirstFirst 12
Results 16 to 18 of 18

Math Help - Vectors help

  1. #16
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,561
    Thanks
    785

    Re: Vectors help

    Express t from one equation and substitute in into the other.
    Follow Math Help Forum on Facebook and Google+

  2. #17
    Newbie
    Joined
    Jul 2011
    Posts
    15

    Re: Vectors help

    Quote Originally Posted by emakarov View Post
    Express t from one equation and substitute in into the other.
    I don't know if this is right but I ended up with b= -2a+7
    Follow Math Help Forum on Facebook and Google+

  3. #18
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,561
    Thanks
    785

    Re: Vectors help

    Yes. Also, you probably got that t = 9 / (4 - a). The latter graph looks like this. So, for a > 4 the time to meeting is negative, which means that the meeting must have been in the past and will not happen in the future (this is natural since if B moves right faster than A, they cannot meet). For a < 4, the function t(a) is increasing. Since we need to find the smallest t, we need to find the smallest allowed a.

    Since the maximum speed of B is 8 km/h, the vector (a, b), when its beginning is at (0, 0), lies inside a circle of radius 8. Also, b= -2a+7. The circle carves a segment on the line b = -2a+7, and we need to take the left end of that segment, which corresponds to the smallest a.
    Follow Math Help Forum on Facebook and Google+

Page 2 of 2 FirstFirst 12

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: November 15th 2011, 06:10 PM
  2. Replies: 3
    Last Post: June 30th 2011, 09:05 PM
  3. Replies: 2
    Last Post: June 18th 2011, 11:31 AM
  4. [SOLVED] Vectors: Finding coefficients to scalars with given vectors.
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: January 23rd 2011, 01:47 AM
  5. Replies: 4
    Last Post: May 10th 2009, 07:03 PM

Search Tags


/mathhelpforum @mathhelpforum