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Homework Help: Compression of spring wrt speed

  1. May 22, 2009 #1
    1. The problem statement, all variables and given/known data

    A block sliding along a horizontal frictionless surface with speed v collides with a spring and compresses it by 2.34 cm. What will be the compression if the same block collides with the spring at a speed of 4.00v?

    2. Relevant equations

    e=0.5mvSUP]2[/SUP] e= 0.5k*x2

    3. The attempt at a solution
    i thought abt equating the two and solving it in regards but there are too many unknown values to cancel them out...and also to find a way to make a connection btw the given information.
    my next thought was to times the given compression by 4 since the speed is also increased but that proved to be wrong..pls. help
  2. jcsd
  3. May 22, 2009 #2

    Doc Al

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    Staff: Mentor

    That should be correct. [edit: At first I said it was wrong, but I didn't read it carefully.]

    Set up a ratio to verify it.
    Last edited: May 22, 2009
  4. May 22, 2009 #3


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    Gold Member

    Equate both energies, potential and kinetic for both systems independently. Then divide the equations against eachother and see what pops out.
  5. May 22, 2009 #4
    ok ...so i'm a little confused abt the divide them against part..so if i do that the k and m would cancel off living (v2+16v2)= (0.0234)2(x2)...does that look right or am i totally off track??
  6. May 22, 2009 #5

    Doc Al

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    Staff: Mentor

    I don't quite understand what you did. Yes, the m and k drop out, but you should have v12/v22 = x12/x22 (or equivalent).

    (Read my correction to my last post.)
  7. May 22, 2009 #6
    ok thanks :))
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