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Need to know how to solve for test

  1. Mar 18, 2009 #1
    A 2.0kg box rests on a plank that is inclined at a angle of 65 degrees above the horizontal. The upper end of the box is attached to a spring with a force constant of 295 N/m. If the coefficient of the static friction between the box and the plank is 0.19, what is the maximum amount the spring can be stretched and the box remain at rest?

    Can someone show me how to complete this problem. The answer is 6.6cm however I don't know to get there. thanks

    I also know that I have to find force and divide that by 295N/M to get answer can someone help me find force please!!!!!!!!!! What numbers do I use
  2. jcsd
  3. Mar 18, 2009 #2


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    Homework Helper

    Get expressions for the forces on the box in the direction of the plank. You'll need to resolve the mg force into a component along the plank and another perpendicular to the plank that you can use to find the friction forces. Set the sum of the forces equal to zero - the point where it will just begin to move. That should allow you to solve for the stretch.
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