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Force of Boxes with Friction

  1. Oct 11, 2011 #1
    A box with a mass of 3.00 kg is at rest on a ramp that is at an angle of 20 degrees with the horizontal. The coefficient of static friction between the box and the ramp is 0.700. Use g = 9.80 m/s2. You now want to make the box move by applying a force. To start the box moving, what is the minimum force you need to apply if your force is directed ...

    (a) perpendicular to the slope?

    (b) horizontally?
  2. jcsd
  3. Oct 11, 2011 #2
    i got part (a) but i'm not sure why it works. mgcos20(mgsin20/static coefficient)

    i still dont know how to do part (b) though.
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