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Homework Help: Box push Forces problem

  1. Apr 6, 2010 #1
    1. The problem statement, all variables and given/known data
    A 10 kg
    box is being pushed up a slippery ramp as shown in Figure 2.1.
    The coefficient of friction between the box and the ramp is just
    μ = 0.1.
    (a) What force does the man need to apply to the box to
    keep it traveling up the ramp at a steady speed?


    2. Relevant equations
    I have attached figure 2.1


    3. The attempt at a solution
    I worked out the normal reaction by finding the vertical component of the normal reaction acting on the box (as =mg) then i found out fmax by fmax = uN
    but my answer is 10N and the actual answer is 27N!!
    what did i do wrong
     

    Attached Files:

    Last edited: Apr 6, 2010
  2. jcsd
  3. Apr 6, 2010 #2
    Are you sure you meant to say 'normal reaction' twice here? I'm a bit confused by your work; what are you taking the horizontal component of?

    Also, what do you mean with fmax? Is that the force the person has to push?
     
  4. Apr 6, 2010 #3
    for this problem you'll want to start out by drawing a force diagram for the box and then applying newton's second law.
     
  5. Apr 6, 2010 #4
    fmax = frictional force
    can somone please show me how to do this its bugging the crap out of me,
    sonic91 arent the forces acting on the box friction and the normal reaction

    mintea;
    the normal reaction is angles because of the inclination, so the upwards force on the box i.e. that acts directly vertically would be the vertical component of the normal reaction i bymistake wrote the horizontal opps heh cheers
     
    Last edited: Apr 6, 2010
  6. Apr 7, 2010 #5
    In that case, your work looks right; you just may be missing a force the man has to work against... I suggest what sonic91 said: put everything on a force diagram and go from there.
     
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