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M2 - Work, Enery, Power question. Help please

Discussion in 'Mathematics' started by parabola, Nov 13, 2011.

  1. I cannot see where I am going wrong with this Question on Work, Energy and Power (from Edexcel Book p80 Q9):
    A parcel of mass 5kg rests on a rough horizontal floor. The coefficient of
    friction between the floor and the parcel is 0.2 The parcel is pulled by a rope
    which is inclined at 10 degrees to the horizontal and the tension in the rope is
    constant and has magnitude 50N.

    a) Find the frictional force.

    b)
    Find the work done by the tension when moving the parcel a distance of
    10m.

    Given the parcel is initially at rest,

    c) Determine the speed
    of the parcel when it has moved 10m.
    I keep getting a) 8.06N, b) 492J and c) 12.8ms-1
    The book's answers are a) 9.8N, b) 492J and c) 12.6ms-1
    I think their answers ignore the vertical component of the tension in calculating reaction force - but I'm not sure why. This is my first year teaching M2 and I don't feel confident enough to just override the book. Please could someone reassure me I haven't totally misunderstood and confirm my amswers or point me in the correct direction if I'm wrong. Thanks
     
  2. DM

    DM New commenter

    Your answers are correct.
     
  3. Thank you.
     

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