Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

experimentX

  • 2 years ago

Q.

  • This Question is Closed
  1. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1350734665748:dw|

  2. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Third case: T = g?

  3. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well ... its g N

  4. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    first case??

  5. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Wait. N = unit?

  6. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes ... tension always has unit of force ... except for surface tension.

  7. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    First case: Σ F = mg mg - T = mg T = 0

  8. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Second case: Σ F = ma mg - T = ma T = m (g-a) = m(g-5) Unit: N for first and second case.

  9. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    But..... but.... but.... the reel.... Shouldn't I take it into consideration??

  10. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you get acceleration after considering the rotational motion of reel. it shouldn't make any difference.

  11. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    in other words you have already taken care of rotational motion of reel. still if you need to verity then ... T*R = torque being applied on reel.

  12. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sorry .. mg*R - TR = torque being applied on reel ... that makes it go round.

  13. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mg*R - TR <--- this part creates motion.

  14. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    acc. of the reel = acc. of the mass?

  15. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no ... the reel does not have linear acceleration. It's rotating ... it has angular acceleration.

  16. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    tangential acc. of the reel = acc. of teh mass?

  17. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes ... maybe ... worth checking it out.

  18. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    If we don't have the acc. of the reel, how can we suppose to find torque, so that we can find tension!?

  19. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well .. we have to find the acceleration reel first.

  20. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    or acceleration of the mass falling down first.

  21. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    But.. how...

  22. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    using conservation of energy \[ {1 \over 2} mv^2 + {1 \over 2}I \omega^2 = mgh \\ \omega r = v,\] solving those two will give you final velocity, you know distance 'd', and initial velocity.

  23. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    solve for acceleration of the using it.

  24. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Wow! We're doing it backward!

  25. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    (c) -> (b) -> (a) :O

  26. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well ...

  27. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    That's not a problem :P

  28. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the other way ... "tangential acc. of the reel = acc. of teh mass" ... at the circumference of reel ... they go foot to foot.

  29. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yes. Then we can find the angular acc. Using integration to find the moment of inertia, and then use it to find the torque. Is it possible?

  30. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yep .. this is also possible.

  31. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For the energy one, can we really use that way?

  32. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    sure ... the torque will always be constant ... hence there will be constant acceleration.

  33. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I'm sorry, but how do I know if the torque is constant?

  34. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the torque depends on two parameters \( r \times F\) , F is part of mgh while r is radius of wheel. both are not changing ... neither is their angle between them.

  35. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mgh?! the PE of the reel or..?!

  36. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hmm?

  37. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    mass .. hold on ... there seems to be discrepancy with second method.

  38. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1350737767080:dw|

  39. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1350737955528:dw|

  40. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Hmm.. So, you're just considering the mass m ..?

  41. experimentX
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1350738106593:dw|

  42. Callisto
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    |dw:1350738529141:dw|