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Unbalances and balanced forces

  1. Nov 26, 2012 #1
    A 13 kg box is placed at the top of a 4.5 m long, ramp inclined at an angle of 41 degrees (with the horizon). However, the ramp is covered with sand so the coefficient of friction is 0.19. How much time does it take the box to reach the bottom of the ramp?

    Fgx=Fg sin=mg sin.

    13kg (9.8 N/kg)=127N

    127N Sin 41= 83N


    4.5m=1/2 (6.4m/s)t^2

    4.5m=3.2m/s t^2
    Im just confused as where the coefficient of friction comes into play, and how to solve it.
  2. jcsd
  3. Nov 26, 2012 #2
    As the box travels down the ramp, there is a frictional force on it and well as the gravitational force.
    Draw the free-body diagram and work out the net force on the box down the ramp.
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