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High school regents problem

  1. Nov 26, 2008 #1
    hi I am new here, but I signed up to ask this question. I was looking at a high school physics exam from last june and one of the questions seems to me like it's unfair. I think they didn't give enough information to solve the problem. here it is;

    An 80-kilogram skier slides on waxed skis along a
    horizontal surface of snow at constant velocity
    while pushing with his poles. What is the horizontal
    component of the force pushing him
    forward?

    (1) 0.05 N
    (2) 0.4 N
    (3) 40 N
    (4) 4 N

    The correct answer is supposedly #3, but I am really unsure why. The problem and the supplied formula tables made no mention to air resistance or friction forces that oppose his forward momentum. If the skier is already at a constant velocity and we neglect any opposing forces, we shouldn't need to apply any extra forces to keep him moving. Am I mistaken?
     
  2. jcsd
  3. Nov 26, 2008 #2

    Doc Al

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    Staff: Mentor

    You're right, the problem seems to be missing some data. Since he's pushing with his poles, friction must be acting. (I presume that no data about the coefficient of friction was given?)
     
  4. Nov 26, 2008 #3

    Doc Al

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    Staff: Mentor

    It turns out that on the official Regents reference sheet, the coefficient of kinetic friction for a waxed ski on snow is given as 0.05.
     
  5. Nov 26, 2008 #4
  6. Nov 26, 2008 #5
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