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Work and Force Question

  1. Oct 8, 2007 #1
    52 kg box is pushed 7.0 meters by a force with a magnitude of 149 N. The coefficient of kinetic friction is 0.25. Determine normal force, force of gravity and frictional force.

    For the normal force I have 52 * 9.8 = 509.6 N Which is also the the force of gravity. However which is positive and which is negative? I assume normal force is positive since it pushes up against gravity pushing downward? Also, how would I convert Newtons into Joules?
  2. jcsd
  3. Oct 8, 2007 #2


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    As long as you are consistent, it doesn't matter which direction is positive or negative. Generally, down is usually taken as negative. Now don't confuse Newtons, a unit of force, with Joules, a unit of energy or work. How much work does each force do on the box?
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