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Force of gravity of chain links problem

  1. Dec 6, 2009 #1
    1. The problem statement, all variables and given/known data
    Two chain links are connected together and are suspended by a string. The mass of the top link, link#1 is 8kg, while the mass of the second/bottom link #2 is unknown. If an applied force on the string attached to link #1 of 216N[up], and the links experience an acceleration of 2m/s^2 [up] find the mass of link #2 and the force that link#2 exerts on link1
    The only given variables we have are
    a= 2 m/s^2
    Fa= 216N
    g=10N

    I'm guessing I have to isolate variables, but im not sure what equations to use.
     
    Last edited: Dec 6, 2009
  2. jcsd
  3. Dec 6, 2009 #2

    Delphi51

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    Re: Forces

    Use F = ma where F is the total of the forces on the object.
    You must be very clear in your mind what "the object" is. The conventional approach is to do an F = ma for each object and the force of one link on the other then will appear in both equations - you get a system of two equations to solve. Sometimes you can reduce the work by cleverly thinking of the two objects combined as one object and use just one F = ma.
     
  4. Dec 6, 2009 #3
    Re: Forces

    Would the total of the forces on the object just be the applied force which is 216?
     
  5. Dec 6, 2009 #4

    Delphi51

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    Re: Forces

    How about gravity?
     
  6. Dec 6, 2009 #5
    Re: Forces

    oh right, so then F, being the total of all the forces would be...
    216N + 10N
    so F=226N
     
  7. Dec 6, 2009 #6

    Delphi51

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    Re: Forces

    No, that 10 N is incorrect. In your first post,
    should read g = 9.81 m/sĀ².
    The force of gravity is mg, which you can't immediately find because you don't know m. Anyway, it is better to stick with symbols like m until you have solved the equation for the quantity you want to find.
     
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