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DLS Group Title

1)A disc has pure rotation.It has angular velocity w.It then comes into contact with a surface which has static friction us,kinetic friction uk and rolling friction ur,When will the disc stop? 2)A disc is placed on the ground.The co-efficient of friction is u,and the co-efficient of rolling friction is u_r.What is the minimum force required to move the disc?The force is applied at the bottom most point

  • one year ago
  • one year ago

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  1. DLS Group Title
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    @Mashy

    • one year ago
  2. DLS Group Title
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    @Mashy

    • one year ago
  3. yrelhan4 Group Title
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    @Mashy @shubhamsrg

    • one year ago
  4. DLS Group Title
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    @Mashy

    • one year ago
  5. DLS Group Title
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    @yrelhan4 @RnR :P

    • one year ago
  6. yrelhan4 Group Title
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    :/

    • one year ago
  7. Mashy Group Title
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    should we consider all the types of friction in question 1? :P.. we can only consider rotational rigth? :D..

    • one year ago
  8. DLS Group Title
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    you will require all 3,when you start the question you will realise :)

    • one year ago
  9. Mashy Group Title
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    but at a time only one friction comes into play.. ! :-/

    • one year ago
  10. DLS Group Title
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    yes..start with static one

    • one year ago
  11. Mashy Group Title
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    but it ll only act for a particular small amount of time.. which i dunno how we could calculate :P

    • one year ago
  12. DLS Group Title
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    :/ okay

    • one year ago
  13. Mashy Group Title
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    and besides i really don't think the static and kinetic have to be considered.. i mean how can you consider static? the wheel is already in rotation .. so no question of static.. and the moment it would come in contact it would start rolling OR slipping.. so only one would come into picture!

    • one year ago
  14. DLS Group Title
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    proceed with whatever u want :/

    • one year ago
  15. Mashy Group Title
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    wait.. rolling friction wouldn't make it stop :D.. it should be the kinetic friction :D

    • one year ago
  16. DLS Group Title
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    arrre kar to :/

    • one year ago
  17. DLS Group Title
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    @Mashy ?

    • one year ago
  18. Mashy Group Title
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    so as i was saying it should be rotational friction itself anyways wat about mass and the radius?!

    • one year ago
  19. DLS Group Title
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    M,R

    • one year ago
  20. Mashy Group Title
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    lol just like tat you grant wishes huh? :D lol

    • one year ago
  21. DLS Group Title
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    assume anything duh

    • one year ago
  22. Mashy Group Title
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    so now there would be a force acting creating a torque that would eventually sue the rolling.. so i guess all you have to do is finde the torque.. then you can find the deceleration!

    • one year ago
  23. DLS Group Title
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    in the end you will get F=-f

    • one year ago
  24. DLS Group Title
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    after applying torque equation n stuff

    • one year ago
  25. DLS Group Title
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    now?

    • one year ago
  26. Mashy Group Title
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    what?!? f = (mur)N/R.... thats the formula for rolling friction right?!

    • one year ago
  27. DLS Group Title
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    /R? upon R?no simply u(r)N

    • one year ago
  28. Mashy Group Title
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    it depends upon the dimensions of mur .. rolling friction can be expressed in both the ways :P

    • one year ago
  29. DLS Group Title
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    abe yr ata hai to kar kya ghante me reply kar rha h :/

    • one year ago
  30. yrelhan4 Group Title
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    ^ Best response. :P

    • one year ago
  31. Mashy Group Title
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    arre sorry.. i was wtching dbz abridged :D..

    • one year ago
  32. wio Group Title
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    Can you draw a picture?

    • one year ago
  33. wio Group Title
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    When it comes to static and kinetic friction, my intuition, and it could be wrong, is that static friction is only meant as a thresh hold to find out whether the object will be moved. Kinetic friction on the other hand is something which applied a resting force over time.

    • one year ago
  34. Vincent-Lyon.Fr Group Title
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    What is your definition of µr (rolling friction coefficient)? It is important, because it is only if rolling friction exists that the disc will eventually come to a halt. Otherwise, it will roll for ever.

    • one year ago
  35. DLS Group Title
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    Your answer is right. I don't have the exact definition of µr (rolling friction coefficient) or even rolling friction. I just know that rolling friction is 1/100th of sliding friction and it depends on hardness of surface. Sorry,ill be glad to get some details about it!

    • one year ago
  36. Vincent-Lyon.Fr Group Title
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    The first phase of the motion is sliding. It is not so straightforward to find the time it will last. The answer is \(\tau_1=\Large \frac {R\omega_0}{3\mu _kg}\) The remaining rotation velocity is \(\omega_1=\Large \frac {\omega_0}{3}\) Velocity of centre of mass is \(v_1=\Large \frac {R\omega_0}{3}\)

    • one year ago
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