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Simple 1D Kinematics Problem

  1. Sep 9, 2008 #1
    1. The problem statement, all variables and given/known data
    In a historical movie, two knights on horseback start from rest 62 m apart and ride directly toward each other to do battle. Sir George's accleration has a magnitude of 0.21 m/s2, while Sir Alfred's has a magnitude of 0.26 m/s2. How far from Sir George's starting point do the knights collide?

    2. Relevant equations

    3. The attempt at a solution
    62 - x = (1/2)*(0.21 m/s^2)t^2
    62 - x = (1/2)*(0.26 m/s^2)t^2

    I was trying to find any velocity or any time but i can't seem to conceive anything logic that would work. Any help would be greatly appreciated.
  2. jcsd
  3. Sep 9, 2008 #2


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    Gold Member

    Try to write equations that give the position of each knight relative to Sir George's starting position at any given time, and then find when they are equal.
  4. Sep 9, 2008 #3


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    Homework Helper

    Almost the right idea.
    You need to use different X1 and x2

    X1 = 1/2a1t2

    X2 = 1/2a2t2

    You know that they meet by definition when the time is equal and ...their total distance adds to 62.

    Divide the first equation by the second.

    You get X1/X2 = a1/a2

    and you know X1 + X2 = 62.
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