Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

ashna Group Title

Is it necessary that work done in the motion of a body over a closed loop is 0 for every force in nature ? why ?

  • 2 years ago
  • 2 years ago

  • This Question is Closed
  1. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    no...it's not true for every force in nature

    • 2 years ago
  2. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    take the example of work done by friction force.

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

    can you first explain the question ? :)

    • 2 years ago
  4. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348895881344:dw|

    • 2 years ago
  5. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    ok

    • 2 years ago
  6. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    there are several forces in the nature..name them...whatever u know.

    • 2 years ago
  7. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    like electric force, magnetic force, spring force, friction force, gravitational force...

    • 2 years ago
  8. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    right?

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

    yeah right

    • 2 years ago
  10. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348896083024:dw|

    • 2 years ago
  11. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    and these are all the closed loops

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

    i have to keep refreshing OS as its goin down , so my replays may seem late n am sry for that ! okay understood.

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

    reply*

    • 2 years ago
  14. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348896151349:dw|

    • 2 years ago
  15. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    now suppose there is a ball situated at point A near the earth

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

    okay

    • 2 years ago
  17. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    and the ball is taken from point A to B to C to D to A..that is ball has been moved on a closed loop during this motion

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

    okay

    • 2 years ago
  19. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348896421255:dw|

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

    yes

    • 2 years ago
  21. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    earth is exerting force mg on the ball...so tell me work done by this gravitational force if ball moves from point A to B...use work done= force* displacement * cos(theta)

    • 2 years ago
  22. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    look for the angle between the force and the displacement

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

    90

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

    cos 90 = 0

    • 2 years ago
  25. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    yes..so work done by gravitational force( A to B)=0

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

    okay

    • 2 years ago
  27. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    our objective is the work done by the gravitational force on the ball so now we come to B to C

    • 2 years ago
  28. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348896858314:dw|

    • 2 years ago
  29. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    ball is moving from B to C again work done by the gravitational force = force*( displacement) *cos(theta) theta=?

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

    0 ?

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

    i mean cos 0

    • 2 years ago
  32. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    there are two vectors..force (mg, vertically downward) and displacement( B to C)..so think carefully for angle between them.

    • 2 years ago
  33. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    displacement ( B to C) is vertically upward.

    • 2 years ago
  34. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348897246563:dw|

    • 2 years ago
  35. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348897411835:dw|

    • 2 years ago
  36. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    does it make sense for visualizing the angle between two vectors pictorially?

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

    yes it does

    • 2 years ago
  38. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so now we come to B to C|dw:1348897603389:dw|

    • 2 years ago
  39. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    got it?

    • 2 years ago
  40. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    force is vertically downward and displacement is vertically upward so angle between them is......?

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

    okay cos 180

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

    -1

    • 2 years ago
  43. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    yes...right..:) so work done by the gravitational force = force*( displacement) *cos(theta) = mg * h * (-1) =-mgh suppose BC=h

    • 2 years ago
  44. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yeah right

    • 2 years ago
  45. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    till now...it's fine?

    • 2 years ago
  46. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yes :)

    • 2 years ago
  47. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    now work done by gravitational force (C to D)= 0 does it make sense?

    • 2 years ago
  48. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yes it does

    • 2 years ago
  49. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348898023808:dw|

    • 2 years ago
  50. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    now we come to work done by the gravitational force on the ball (D to A) tell me how much it'll be?

    • 2 years ago
  51. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    just look for angle between gravitational force and displacement when ball moves from D to A

    • 2 years ago
  52. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    cos 0 ?

    • 2 years ago
  53. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    yes

    • 2 years ago
  54. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so work done by the gravitational force on the ball (D to A)= mg* h* cos(0)= mgh BC=DA=h

    • 2 years ago
  55. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    okay

    • 2 years ago
  56. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so our objective has been completed...I mean...we have calculated...work done by gravitational force on the ball when the ball moved on a closed loop.

    • 2 years ago
  57. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yes !

    • 2 years ago
  58. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so total work done= W(A-->B) + W(B--->c) + W(C--->D) + W(D--->A) =0 + (-mgh) + 0 + mgh =0

    • 2 years ago
  59. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so work done by gravitational force in the motion of a body over a closed loop is 0.

    • 2 years ago
  60. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    okay understood , and why is this not the same for every force in nature ?

    • 2 years ago
  61. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    but we took a rectangular loop for a closed loop..one can show this for any arbitrary|dw:1348898826574:dw| closed loop

    • 2 years ago
  62. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    but it's not true for every force in nature...e.g. friction force

    • 2 years ago
  63. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    and why ?

    • 2 years ago
  64. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so we classify the forces into two type if work done by the force over a closed loop is zero then conservative force otherwise non-conservative force

    • 2 years ago
  65. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    i don't understand , why not for frictional force ?

    • 2 years ago
  66. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    yes...I am coming there

    • 2 years ago
  67. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    okay :)

    • 2 years ago
  68. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    1st have a look...why not zero?|dw:1348899134273:dw|

    • 2 years ago
  69. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    suppose there is a block of mass m moves on a rectangular loop, and the loop is kept horizontally on the earth

    • 2 years ago
  70. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    like before , okay !

    • 2 years ago
  71. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348899311394:dw|

    • 2 years ago
  72. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    do u agree that work done by the friction force on the block will be negative in each segment(AB, BC,CD,DA) of this loop?

    • 2 years ago
  73. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    because during motion, angle between friction force and displacement will be 180'

    • 2 years ago
  74. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    am sorry but i did not understand the last part !

    • 2 years ago
  75. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    which one...do u agree that work done by the friction force on the block will be negative in each segment(AB, BC,CD,DA) of this loop?

    • 2 years ago
  76. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    yes the same

    • 2 years ago
  77. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    ok...1st we'll see the work done by the friction force on the block,when it moves from A to B again work done= force*( displacement)* cos(theta) theta=?

    • 2 years ago
  78. ashna Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    90

    • 2 years ago
  79. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348899953137:dw|

    • 2 years ago
  80. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    |dw:1348900005470:dw|

    • 2 years ago
  81. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    see..if block moves from A to B then displacement of block =AB...right?

    • 2 years ago
  82. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    direction of displacement is to the right and the direction of friction force is to the left

    • 2 years ago
  83. akash123 Group Title
    Best Response
    You've already chosen the best response.
    Medals 2

    so again there are two vectors friction force and displacement...look for the angle between them carfully

    • 2 years ago
  84. sam291 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    But when it moves from C to D the direction of the force vector is opposite from the direction from A to B, so it will still add up to zero going around the loop. Am I wrong?

    • 2 years ago
  85. kappa007 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    Forces in nature can be either conservative or non-conservative. Work done in a closed loop by a conservative force is always 0 .

    • 2 years ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.