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Homework Help: Someone please help me with these symbols?

  1. Mar 29, 2012 #1
    1. The problem statement, all variables and given/known data

    I'm doing an impact physics for engineering question and I cannot tell the difference between

    (v_A)_2x & (v_(Ax))_2.

    * I don't think I'll need help with solving the actual question if I understand these variables.

    2. Relevant equations


    3. The attempt at a solution

    I know that v_A is object A's initial velocity, however, I don't know how to deal with the _2x. As for the second term above, I have no idea.....
  2. jcsd
  3. Mar 29, 2012 #2


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    Staff: Mentor

    Welcome to the PF.

    Can you post a picture or scan of the use of those symbols?
  4. Mar 29, 2012 #3


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    welcome to pf!

    hi c0nfused34235! welcome to pf! :smile:

    (try using the X2 button just above the Reply box :wink:)

    you mean (vA)2x & (vAx)2 ?

    what is the context? :confused:
  5. Mar 30, 2012 #4
    Hi guys, thanks for the warm welcome and quick replies. Here's the question and it's solution. I was trying to figure it out (how they solve it) and I could not understand how they found the 2 variables in the red box (see image attached below). Thanks again.

    Attached Files:

  6. Mar 30, 2012 #5


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    Staff: Mentor

    (v_A)2 is the final velocity of body A, i.e., its velocity after the collision

    (v_A)_2x is the x-component of body A's final velocity after collision

    (v_(Ax))_2 is the after collision value of A's x-component of velocity

    The sum of the x-components of momentum of the system before and after the bodies collide remains constant. The same goes for the y-components of momentum.
  7. Mar 30, 2012 #6


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    hi c0nfused34235! :smile:
    (vA)2x and (vAx)2 are the same

    (i've no idea why they've done that :redface:)

    so they just add (vA)2x + (vB)2x to (vA)2x - (vB)2x to get 2(vA)2x

    (and subtract to get 2(vB)2x) :wink:
  8. Mar 30, 2012 #7
    Could someone please solve for one of them (with steps)? I still don't understand how they solve for those variables. If they are indeed identical, why can't I substitute one set into the other formula? I get completely incorrect values.
    Last edited: Mar 30, 2012
  9. Mar 30, 2012 #8
    YES I GOT IT!!!

    Thanks for your help guys!
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