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Simple vector problem

  • Thread starter ohheytai
  • Start date
  • #1
85
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i uploaded it i cant figure out r subscript n i have no idea can someone help me its my last try thanks
 

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  • #2
31
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It says that [itex]r_{n}[/itex] and [itex]r_{a}[/itex] give the position with respect to the origin, while r is a relative position vector.

So what vectors would [itex]r_{n}[/itex] and [itex]r_{a}[/itex] be if they start at the origin? Where would the end of those vectors lie? Given that [itex]r = r_{n} - r_{a}[/itex].
If the answer isn't obvious then review material on graphically subtracting vectors.
 
  • #3
85
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i only have the vector sum though and i dont have those two vectors
 
  • #4
1,137
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Note that in a displacement vector r = ra - rb

ra is the vector from origin to head of the vector r
and rb is vector from origin to tail of vector r
 

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