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Newton's laws of motion -- pulley system

  1. Jun 28, 2017 #1
    1. The problem statement, all variables and given/known data
    In the situation given all surfaces are friction less pulley is ideal and steering is light. Find accn of block 2

    2. Relevant equations
    Given F=mg/2

    3. The attempt at a solution.
    Got answer as G/2 instead of G/4 ...(actual answer is g/4)
    Since F=mg/2 and block 1 is hanging so acceleration shld be g/2 of block 1 and therefore acceleration of Block 2 shld g/2.
     

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    Last edited by a moderator: Jun 28, 2017
  2. jcsd
  3. Jun 28, 2017 #2

    Orodruin

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    i do not understand your argumentation. Can you spell it out with more detail?

    The correct answer is g/4.
     
  4. Jun 28, 2017 #3
    Yes sure...Im not getting the answer as g/4... instead im getting g/2 ...i am maybe wrong at some point but i can't figure out where
     
  5. Jun 28, 2017 #4
    Yes sure...Im not getting the answer as g/4... instead im getting g/2 ...i am maybe wrong at some point but i can't figure out where
     
  6. Jun 28, 2017 #5

    Orodruin

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    Yes you are wrong, which is why I asked you to expand your reasoning so that it might be apparent where your logic fails. As it stands, it is very difficult to follow your logic.
     
  7. Jun 28, 2017 #6
    Oh ok sure,My logic say that acceleration of pulley equals acceleration of the block 2(pic) and acceleration of pulley is a2-a1 but this gives me answer as g/2..
     
  8. Jun 28, 2017 #7
    But this logic is incorrect right?
     
  9. Jun 28, 2017 #8

    Orodruin

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    What is a1 and a2? You mist define things before you can use them. What are they and what values would they take. Please work on spelling out your thoughts. You have so far just briefly described your thoughts, not really motivated why you think some relations should hold.
     
  10. Jun 28, 2017 #9
    a2 is the force and a1 accn of block 1
    I think that since surface is massless the magnitud that pulley accelerate will be same as the magnitude block 2 accelerates since there are no other force acting on the body..
     

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  11. Jun 28, 2017 #10
    Can you please explain your logic...i m pretty confused after this
     
  12. Jun 28, 2017 #11

    Orodruin

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    Let me stop you right there. Force and acceleration have different physical dinension. It makes no sense whatsoever to take a difference between a force and an acceleration.

    What surface? Which body? Please take the time to gather your thoughts and write a self-contained argument. We are not mind readers ... What is your free body diagram and what conclusions can you draw from it?

    It is also unclear from your picture what a1 and a2 are the accelerations of and in which directions they go.
     
  13. Jun 28, 2017 #12
    NVM leave it... I'll apply my mind or ask my teacher.
    Thnx a lot for your precious time..
     
  14. Jun 28, 2017 #13

    Orodruin

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    I think you might have a misconception of what this forum is for. Nobody here will spoon feed you answers. What we can do is to help you think in the right direction, but in order to do so you must be able to gather and present your thought process. You were always going to have to do dome thinking on your own, it is the only way to learn.
     
  15. Jun 30, 2017 #14
    I
    Got that soln myself sir... Just had a miscommunication which made me impatient
     
  16. Jun 30, 2017 #15
    I already know what this forum is for and I know that i hv to be within those guidelines no matter what..."This is the way i will learn!"
     
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