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Homework Help: Frictionless inclined plane physics homework

  1. Nov 20, 2005 #1

    IB

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    A 2.0 kg mass slides down a frictionless inclined plane that makes an angle of 30 degrees with the horizontal. The sass starts from rest. What is its speed after it has slid a distance of 3.0 m along the incline?

    I got:

    F = (sin30)(9.8)
    F = 4.9 N

    W = Fd
    W = (4.9) (3) = 14.7 J

    W = E_kin
    14.7 J = 1/2 mv^2
    v = 1.21 m/s

    Is my method correct? I'm very unsure how to do this one. Thanks.
     
  2. jcsd
  3. Nov 20, 2005 #2

    lightgrav

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    Homework Helper

    your Work-Energy method is excellent ...
    but a few chapters ago, F = M g sin (theta)
    . . . if you had USED units [kg N/kg] you would have caught your error.
     
  4. Nov 20, 2005 #3

    IB

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    F = M g sin (theta) ?

    I'm not sure what you mean. :confused:
     
  5. Nov 21, 2005 #4

    daniel_i_l

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    Gold Member

    you forgot the mass when you calculated the force.
     
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