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Block, Ramp, Friction, and Spring

  1. Oct 12, 2008 #1
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    A man pulls a block of mass m = 19 kg up an incline at a slow constant velocity for a distance of d = 6 m. The incline makes an angle q = 32° with the horizontal. The coefficient of kinetic friction between the block and the inclined plane is µk = 0.2.

    a) What is the work Wm done by the man?
    I got Wm =782.31

    At the top of the incline, the string breaks and the block, assumed to be at rest when the string breaks, slides down a distance d = 6 m before it reaches a frictionless horizontal surface. A spring is mounted horizontally on the frictionless surface with one end attached to a wall. The block hits the spring, compresses it a distance L = 0.4 m, then rebounds back from the spring, retraces its path along the horizontal surface, and climbs up the incline.

    b) What is the speed v of the block when it first reaches the horizontal surface?

    c) What is the spring constant k of the spring?

    d) How far up the incline d1 does the block rebound?


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



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 12, 2008 #2

    Hootenanny

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    You can attempt this question in one of two ways: energy conservation or forces analysis.
     
  4. Oct 12, 2008 #3
    Ok, well which do you recommend?
     
  5. Oct 13, 2008 #4

    Hootenanny

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    Personally, I always find conservation of energy the most straight forward.
     
  6. Oct 13, 2008 #5
    Ok well some recommended I try v = sqrt 2(gh- ug cos 33), but that didn't work so now I'm lost again. How should I apply conservation of energy here?
     
  7. Oct 13, 2008 #6

    Hootenanny

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    What does the principle of conservation of energy (COE) state? Can you use COE to write down an equation for part (b)?
     
  8. Oct 13, 2008 #7
    Ok so using COE I was able to figure out the the Wg+Wf = KE at the bottom and setting that equal to .5mv^2 I got v = 6.51.

    Now I'm trying to solve for K when the spring is compressed. I know that at this point all the energy is in the spring so I thought KE = -k(x2^2 - x1^2)/2. So I did 403.04 = - k(0.6^2)/2 but that didn't work. Anyone know what I did wrong?
     
  9. Oct 14, 2008 #8

    Hootenanny

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    Are you sure about that equation? How much energy does the block have at the top of the incline?
     
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