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Finding Spring with kinetic friction involved

  1. Apr 20, 2012 #1
    Hello everyone, i have the following two part prompt and im having a difficult time with the second part. Here is first part of the prompt,

    A block of mass 0.528 kg slides with uniform velocity of 4.15 m/s on a horizontal frictionless surface. At some point, it strikes a horizontal spring in equilibrium. If the spring constant is k = 25.5 N/m, by how much will the spring be compressed by the time the block comes to rest?

    I found the spring compression to be 0.59m using Energy(initial)+Work(non conserved)= Energy(Final)

    The second part is as follows,

    What is the amount of compression if the surface is rough under the spring, with coefficient of kinetic friction µk = 0.411?

    From what i learned in class i am supposed to stick to the concept used above, so I plugged in Kinetic friction for work as '-0.411d'. My professor made it known that d stood for the distance but I'm not sure where I can pull that information.

    I tried using 0.59 since that 'was' the distance travelled before friction was introduced but it didn't work out.

    Any help would be appreciated.
     
  2. jcsd
  3. Apr 20, 2012 #2

    Doc Al

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    Staff: Mentor

    Your expression for the work done by friction is incorrect. Given the coefficient of friction, what's the force of friction?
    You're going to solve for the distance, so set up an energy equation with d as the unknown.
     
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