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Homework Help: Energy to drag a block

  1. May 15, 2009 #1
    1. The problem statement, all variables and given/known data

    whats the energy required to drag a block a distance L

    2. Relevant equations

    coefficiant of friction between block and floor = [tex]\mu[/tex]
    density of block = p

    force*distance = change in kinetic energy

    3. The attempt at a solution

    friction acting against movement Fr = [tex]\mu[/tex]mg m = mass of block

    force in direction of movement F = ma

    resultant force = F - Fr = m(a-[tex]\mu[/tex]g)

    resultant force*L = energy = m(a-[tex]\mu[/tex]g)L

    i dont think the last step is right though as im not sure sure that the assumption made that energy required is the same as the change in KE is correct...

    help or guidance appreciated
  2. jcsd
  3. May 15, 2009 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Although not stated as such, I think you are looking for the energy (work) required by a person or machine to just overcome friction and move the block at constant speed (no acceleration).
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