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Finding a Tension Ratio

  1. May 4, 2009 #1
    1. The problem statement, all variables and given/known data
    A clay ball of mass m hangs from a string with length L. When a second clay ball with mass 2m approaches it with a speed of sqrt(2gL) on the same plane. The collision is completely intelastic so that the balls stick together after the collision. Let T1 be ethe tension in the string immediately after the collision and T2 be the tension in the string when the combined balls are at their maximum angle X. Find T2/T1.
    The known quantities are m, g, and L

    the answer is supposed to be : 5/17

    2. Relevant equations
    m1V1+m2V2=(m1+m2)Vimp
    E1 + Work Non Conservative= E2
    any Force summations


    3. The attempt at a solution
    ok so I started out with momentum conservation.
    since the mass m is at rest I threw that out of the left side of the eqn.
    so I get:
    2m(rt[2gL]) = (3m)Vimp
    so I conlculded that the impact velocity (Vimp)= 2/3of(rt[2gl])

    I then did FBDs for the initial and at the top of the swing.
    at the bottom I got that
    T1-3mg = (3mVimp/L)
    and at the top of the swing
    T2-3mgcosX = 0 (im not sure about this but I dont think it's accelerating radially if it hits absolute max swing angle since it would be at rest would it not at that instance?"

    I then did energy conservation:
    E1+Wnc=E2
    I defined my y=0 to be the plain that the initial balls were traveling in. I got the ff:
    E1 + Wnc:
    K=(1/2)3mVimp^2
    U=0
    W=T1Lcos0 (again not sure)
    E2:
    K=0
    U= 3mg(L-LcosX)

    I don't know how to approach the problem given what I've found out. Thank you soo much for your guys' help in advance. Oh and sorry for the crazy notation Im using. I've had to make some compromises since I dont know how to do greek lettering and such on the comp :).
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 4, 2009 #2
    sorry for the double post but I dont know if this will help but here is the visual. Its problem number 2 on my practice test. Thanks again
     

    Attached Files:

  4. May 4, 2009 #3
    anybody? I really need help on this one. I have a test in 2 hours.
     
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