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Block, Ramp, Friction, and Spring

  1. Oct 18, 2009 #1
    A man pulls a block of mass m = 20 kg up an incline at a slow constant velocity for a distance of d = 3.5 m. The incline makes an angle q = 29° with the horizontal. The coefficient of kinetic friction between the block and the inclined plane is µk = 0.3.

    a) What is the work Wm done by the man? Wm = 513.1

    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 = 3.5 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 = 0.6 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? v = 3.91
    c) What is the spring constant k of the spring? k = 849.3
    d) How far up the incline d1 does the block rebound? d1 = ?

    For picture: https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2111/fall/homework/Ch-08-GPE-ME/block_ramp_friction_spring/9.gif [Broken]

    W = ΔKE, W = F*d, U = m*g*h

    So I'm stuck on part d.). I thought I could do U = KE - W(friction) = (((1/2)m*v^2) - μmgh*cos(29)) / mg = 0.517 but that didn't work. Any help please?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Oct 18, 2009 #2


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    There is no mention of spring in the problem. How is that?
  4. Oct 18, 2009 #3
    Sorry my bad, I've added the rest of the info after part a.), I've also added a link to the picture included.
  5. Oct 18, 2009 #4


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    Angle of the inclined plane is not given. Whether d is the displacement along the inclined plane?
  6. Oct 19, 2009 #5
    Yes it is.

  7. Oct 19, 2009 #6


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    While going up the kinetic energy of the block = work done against (frictional force + component of weight in the downward direction) + PE.
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