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Radius vectors

  1. Sep 11, 2007 #1
    what do radius vectors of particles really mean and how can they be at a different angle with velocity v.
  2. jcsd
  3. Sep 11, 2007 #2
    The radius vector [tex]\vec{r}[/tex] is the vector from some origin to the position of the particle at some time [tex]t[/tex]. Typically, [tex] \vec{r}(t)[/tex] is the trajectory, so to speak of the particle, so the derivative with respect to time is the velocity: [tex] v_t = \frac{d\vec{r}}{dt}[/tex]. Because the position is constantly changing, the velocity as well as the angle changes with respect to the origin.

    Does that answer your question?
  4. Sep 11, 2007 #3
    Consider yourself at the origin of a coordinate system. Any vector connecting you with an object is radial. That object may change its position, shown by a velocity vector, which is often not along the radial vector.

    For instance, although motion along a circle is confined to a given radial distance out from the center, velocity is restricted to move tangent to the circle, and the acceleration enforcing circular motion orients radially toward the center!
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