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Homework Help: Kinetic Energy with diagram

  1. Nov 27, 2007 #1
    Kinetic Energy with diagram!!!

    1. The problem statement, all variables and given/known data

    In the figure below, a small block is sent through point A with a speed of 7.5 m/s. Its path is without friction until it reaches the section of length L = 12 m, where the coefficient of kinetic friction is 0.70. The indicated heights are h1 = 6.5 m and h2 = 1.6 m.

    (a) What is the speed of the block at point B?
    (b) What is the speed of the block at point C?


    2. Relevant equations

    Friction force=mu*force normal

    3. The attempt at a solution

    First off, ignore the friction stuff because I already got those. I just need help with the 2 specific questions I listed. For a I did K=U so I set .5v^2=gh since the masses cancel out. But I got velocity and it was wrong...
  2. jcsd
  3. Nov 27, 2007 #2
    Ooo! I did this one a while back.

    Ok the reason you missed the first one is because U @ point a does NOT equal K @ point B. U+K @ a does though. Don't forget it's initially moving.
  4. Nov 27, 2007 #3
    So U+K(point A)=K(point B)?
  5. Nov 27, 2007 #4
    what's point d in there for then, lol
  6. Nov 27, 2007 #5
    It's for another part of the problem I already figured out so don't worry about it lol.
  7. Nov 27, 2007 #6
  8. Nov 27, 2007 #7
    indeed. the second question is similar. Energy total @ point b = energy total @ c

    Ergo... K(@b)=U+K(@c)
  9. Nov 27, 2007 #8
  10. Nov 27, 2007 #9
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