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Incline plane and acceleration

  1. Nov 2, 2008 #1
    The problem statement, all variables and given/known data[/b]
    Objects of Masss m1= 4kg and m2 = 9kg are connected by a light string that passes over a frictionless pulley. Object m1 = is held at rest on the floor, and m2 rests on a fixed incline of 40 degrees. The objects are released from rest, and m2 slides 1 meter down the <b>rough</b> incline in 4 seconds.
    a) determine the acceleration of each object using a kinematic equation for constant acceleration b) the tension in the string, and d) the coefficient of kinetic friction between m2 and the incline.

    I'm really having trouble finding the acceleration, I'm not sure if I am looking too deeply into it.
  2. jcsd
  3. Nov 2, 2008 #2


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    Welcome to PF!

    Hi leisiminger! Welcome to PF! :smile:

    Is the incline a ramp that leads upward to the floor? :confused:

    If not, can you explain the set-up?

    Anyway, tell us what principles you've tried, and where you're stuck, and then we'll know how to help. :smile:
  4. Nov 2, 2008 #3
    Re: Welcome to PF!


    is a good picture of the problem, except that m1 starts on the floor at rest.

    well, to be honest, i thought about just analyzing one block, since accleration will be the same on both blocks, using a = Vf-Vo / t. Vf being .25 m/sec ( 1 m / 4 sec ), Vo being zero, and time being 4 sec.

  5. Nov 2, 2008 #4


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    Hi leisiminger! :smile:

    I think you'll have to do an equation for each block, and combine them to get your kinematic equation.

    Hint: call the acceleration a, and the tension T. :smile:
  6. Nov 2, 2008 #5
    i dont understand, the acceleration of one block should be the acceleration of the other block right? The velocity of an object under constant acceleration will increase linearly and is:
    vf = v0 + a t
  7. Nov 2, 2008 #6


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    oh I see what you're doing :redface:

    yes, if you assume the acceleration, a, is constant, then you can calculate a without using m1 m2 or theta …

    but you need an equation with s and t, not v and t. :wink:
  8. Nov 2, 2008 #7
    any more help, just a clue?
  9. Nov 2, 2008 #8


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    oh come on

    s = … ? :smile:
  10. Nov 2, 2008 #9
    we use a,v,x,and t. i assume your mean x for change in distance? if so, its 1m
  11. Nov 2, 2008 #10
    ok, i have an idea. would i use

    a = m1g -m2gsin theta
    m1 + m2
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