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Physics:Incline planes

  1. Apr 5, 2007 #1
    A weightless pulley is attached to the top of an inclined plane which makes an angle of 30degree with the horizontal.Masses A and B,each of mass 1kg,are joined by an inextensible string passing over the pulley.Neglecting frictional forces,calculate the accleration of the masses and the tension in the string.(Shows working thanks)

    My working:
    let m2 be mass of b,m1 be mass of a.Assuming acceleration due to gravity to be 10m/s².
    m2g - T = m2a ---(1)
    T - sin30m1g = m1a ---(2)
    Substituting the values from the question,i have
    From (1): 10-T=a ---(3)
    From (2): T-5=a ---(4)
    Substitute (3) into (4):
    Substituting T into (3),

    Further Details
    The answers given to me was 2.5m/s² for acceleration and 75N for tension.
    Is the answers correct?
    If yes,any clues to get 75N?
    Thanks for replying.Appreciates it.
    Last edited: Apr 6, 2007
  2. jcsd
  3. Apr 5, 2007 #2


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    method looks good to me. is there a problem?
  4. Apr 6, 2007 #3


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    Gold Member

    I would agree with mjsd, your method looks correct. I would suggest that the given answer is a typo and should read 7.5N as you have.
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