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Motion in 2 Dimensions - Inclined Plane Pulleys

  1. Mar 31, 2008 #1
    1. The problem statement, all variables and given/known data
    a Mess of 5kg is being hauled up a smooth invlined place at 30 degree to the horizontal with an acceleration of 1.5ms^-2 by mean of a string parallel to the incline:
    a) What is tension in the string

    2. Relevant equations
    Fnet= ma
    Rules of right angled triangles (SOC CAH TOA)
    Any more?

    3. The attempt at a solution
    =>Fnet = ma
    Fnet = 5*1.6
    Fnet = 8ms^-2
    =>cos(theta)= O / H
    cos60= O / 8
    Tension = 16N = Wrong!
    Answer = 32.5 N - How??
  2. jcsd
  3. Mar 31, 2008 #2


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    The weight has 2 components, one is perpendicular to the plane, the other is down the plane. The tension acts up the plane. So the resultant force up the plane is?

    (Also,the component down the plane is always weight*sine of the angle of inclination. Not cos)
  4. Apr 1, 2008 #3
    2 Components. interesting..
    That means the Perpendicular component
    => Fnet = ma
    => Fnet = 5*9.8
    => Fnet down = 49N

    What next?
  5. Apr 1, 2008 #4
    Before you approach questions like these, you must have a great understanding of how to draw freebody diagrams. For this question, Fnet = Ft + (-Fg parallel) = ma. If you do not understand where these forces are coming from, let me know and I'll draw you the freebody diagram.
  6. Apr 1, 2008 #5
    Here, I attached a freebody diagram for the following question given that there is no force of friction due to the emphasis of a smooth surface and no coefficient of friction was given. Can you identify which forces are involved?

    Attached Files:

  7. Apr 1, 2008 #6
    Well I know that there are two main forces acting upon the pulley.

    | Resistance Forces/ Tension

    \|/ Gravity = 9.8ms Accel

    These are the two I can think of, is there any more?
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