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Particles moving along the axes.

  1. Sep 8, 2007 #1
    Particle 1 is moving on the x-axis with an acceleration of 5.45 m/s^2 in the positive x-direction. Particle 2 is moving on the y-axis with an acceleration of 7.56 m/s^2 in the negative y-direction. Both particles were at rest at the origin at t = 0 s. Find the speed of particle 1 with respect to particle 2 at 6.15 s. Answer in units of m/s.

    I'm not sure what the question is asking for. The whole "with respect to" slightly confuses me. In the x-direction, the velocity after 6.15 is 33.5175. In the negative y-direction, it is 46.494. ...am I just suppose to draw the hypotenuse to the triangle formed and find that length?
  2. jcsd
  3. Sep 8, 2007 #2


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    Science Advisor

    Yes. The velocity of #1 with respect to #2 is [tex]\vec{v}_1-\vec{v}_2[/tex]. Since [tex]\vec{v}_1[/tex] is perpendicular to [tex]\vec{v}_2[/tex], the speed (which is the magnitude of [tex]\vec{v}_1-\vec{v}_2[/tex]) is [tex](v_1^2+v_2^2)^{\scriptstyle{1/2}}[/tex].
  4. Sep 8, 2007 #3
    Thank you!
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