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Is it possible to find the tension force without mass?

  1. Oct 30, 2014 #1
    1. The problem statement, all variables and given/known data
    The system to the right has two identical masses. (one is hanging off the ledge of a table, one is on the table, they are connected by a rope.) tge coefficients of kinetic and static friction are .54 and .63 respectively. Find the acceleration and the tension in the rope. (No masses are given, just that they are equal, and we ignore the mass of the rope and friction of the pully.



    2. Relevant equations
    I found the acceleration no problem, however the tension force eludes me and my teacher. (I should note that this isn't my homework, it was from another school and someone from there showed it to me. Me and my teacher were very confused and have spent days trying to figure it out.). Is there any way to find the tension force without the need for mass? If there is any way, even beyond what we would have learned by now in AP Physics then please tell me, but if there is a way to do it using just forces and kinematics then even better. Thanks!



    3. The attempt at a solution
    We've tried breaking down ewuations and everything to find a solution without mass but have not come up with anything.
     
  2. jcsd
  3. Oct 30, 2014 #2

    Orodruin

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    Is it possible to construct any quantity with the units of a force using your input variables?
     
  4. Oct 30, 2014 #3
    The only things that are given are the masses are equal, and the friction forces. You also know the gravitational acceleration but that doesn't get s numerical answer, all we could get was F=9.8m but I want a numerical value for the tension force
     
  5. Oct 30, 2014 #4

    Orodruin

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    Yes, that is all you will be able to do. What I am trying to explain is how you can see that it is impossible to get a definite value without knowing the mass.

    So what are the units of the following quantities?
    The friction coefficients
    The gravitational acceleration
    The ratio between the masses
    The tension in the string
     
  6. Oct 30, 2014 #5
    That's what I had been asking, if it was possible to find it. The coefficients of friction are static = .63 and the kinetic = .54, the gravitational acceleration is 9.8m/s^2, ratio between the masses js 1:1, and the tension on the rope is what I have been asking about.
     
  7. Oct 30, 2014 #6

    Orodruin

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    Yes, but what I am asking is whether or not you know which units those quantities are measured in, e.g., acceleration as you say is measured in m/s^2.
     
  8. Oct 30, 2014 #7
    Can you show the picture of the system?
     
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