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Adding magnitude of vector

  1. May 27, 2009 #1
    1. The problem statement, all variables and given/known data

    A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of this sum might be:
    A. Zero
    B. 3
    C. 12
    D. 47
    E. 50


    2. Relevant equations

    Probable the Pythagoreans and use of sin, cos, etc.

    3. The attempt at a solution

    Not sure how to add the magnitude of vector w/out knowing the angle or the different components.



    Thanks for looking at the problem.
     
  2. jcsd
  3. May 27, 2009 #2

    LowlyPion

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    Welcome to PF.

    Maybe eliminate the answers that aren't possible?
     
  4. May 27, 2009 #3
    I know what the answer it. I just don't know how the answer key got there. There are some rules that constrain the addition/subtraction of magnitude of vectors, but I don't know what they are. I am searching the net but to no avail.


    P.S
    Thanks for the welcome.
     
  5. May 27, 2009 #4

    rock.freak667

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    If you have those two force acting on a body, when would the resultant force be maximum and when would they be minimum?
     
  6. May 27, 2009 #5

    LowlyPion

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    You know that depending on direction a vector can be added head to tail right? So the biggest value the result can be is ... |20| + |25|

    Likewise the smallest value the result can be is when they are in opposite directions. |25| - |20|

    Looks like there is only one answer that satisfies these conditions.
     
  7. May 29, 2009 #6

    Yea, this was the rule I was looking for. Thanks a lot Pion.
     
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