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Homework Help: Calculating Ek At a specific point

  1. Nov 8, 2008 #1
    1. The problem statement, all variables and given/known data

    I need to find out the Ek at "B" this is the diagram i got i want to know if its right and if it is why do i use the Height of 50 to find out Ek at "B"

    phys.jpg

    2. Relevant equations

    Ek=Ep

    3. The attempt at a solution

    Ek=Ep
    Ek=m.g.h
    Ek=100x9.8x50
    Ek=49000J
     
  2. jcsd
  3. Nov 8, 2008 #2

    tiny-tim

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    Welcome to PF!

    Hi Articulum! Welcome to PF! :smile:
    Yes, that's right! …

    (except it's really change in Ek = change in Ep) …

    but why were you worried about using 50 for B? :smile:
     
  4. Nov 8, 2008 #3
    Re: Welcome to PF!

    If i'm figuring out Ek at "B" shouldn't i use the height also at "B"?
     
  5. Nov 9, 2008 #4
    The *change* in kinetic energy plus the *change* in potential energy equals zero here: so you do need to use the height at B, or more precisely, what matters is the *difference* in height between A and B.

    Probably the picture is badly drawn, I suppose the difference in height between A and B is 50m [the units for height are missing, too].
     
  6. Nov 9, 2008 #5
    So i use the Diffrence in height of where it starts and where the point is?
     
  7. Nov 9, 2008 #6
    Exactly!
     
  8. Nov 9, 2008 #7
    Thank you so much made my Physics work much easier
     
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