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Homework Help: Rotational: angular momentum

  1. Oct 17, 2016 #1
    1. The problem statement, all variables and given/known data

    a spool of radius R1 and R2 (R2>R1) is kept on hortizontal surface. A force f= 2t N (where t is time ) acts on the inner radius tagentially find the angular momentum of the system about the bottomost point of the spool.
    2. Relevant equations

    3. The attempt at a solution
    but the answer is t^2(R1+R2)
  2. jcsd
  3. Oct 17, 2016 #2
    Where is the pool fixed at the center or at the indicated point?
  4. Oct 17, 2016 #3
    It's not fixed ...it's on the floor free to rotate and translate
  5. Oct 17, 2016 #4
    Frankly, your work is illegible.

    Nonetheless, could you give me the relation between ## \vec v## and ##\vec a##, and that between ##\vec α## and ##\vec ω##?
  6. Oct 17, 2016 #5
    I solved it just used the wrong equations ...!
  7. Oct 17, 2016 #6
    but can you please solve iit jee paper 2 2016 rbd question
  8. Oct 17, 2016 #7


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    Science Advisor
    Homework Helper
    Gold Member

    In your calculation of the linear acceleration you have ignored friction at the ground. Not sure if you did the same with the moments.
    Please do not post working as images. Use images for diagrams and textbook extracts. Take the trouble to type in your algebra.
  9. Oct 17, 2016 #8
    I solved it
  10. Oct 19, 2016 #9
    You say F = 2t what about direction? Then you want angular momentum at what time. If time varying force is acting neither the momentum nor angular momentum will be constant.
  11. Oct 19, 2016 #10
    Thanks for the reply but I solved it
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