A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

TrojanPoem

  • one year ago

Statics: A metal homogeneous opaque ball with radius r was fastened from a point on its surface with a robe and the other end was fastened on point (A) on a rough vertical wall, the ball stationed in balance and It was about to slip down the wall at point (B). If AB = sqrt(3) r and the friction coefficient between the ball and wall is 1/sqrt(3).Prove that the tan of the angle which the robe makes with the wall is sqrt(3)/2 notice that the the action line of the ball weight affects on it's center.

  • This Question is Closed
  1. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    what is the form for rotational intertia

  2. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    you should have just drawn it :P

  3. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I though you'd prefer to draw it yourself :D

  4. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435161429650:dw|

  5. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I can't add the lengths or the drawing will be nasty.

  6. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    woah okay, this is confusing drawing

  7. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    where is the horizontal wall?

  8. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Notice that : Fg = weight of the ball Fb = force of pulling in the robe m = friction coefficient r = reaction of the wall

  9. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    typo not horizontal but vertical.

  10. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okay lemme try drawing it and see if i got this right

  11. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435161896312:dw|

  12. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okay so our normal force is Fb* sin theta

  13. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    did you say the resistance force are both from the frictional + moment of intertia

  14. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    When the ball tries to slip , friction force will be generated = reaction of the wall x friction coefficient it's similar to this : |dw:1435162343747:dw|

  15. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yes u also have to account for the resistive interial force, trying to remmber how to apply that again

  16. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    both of these will aid in lowering FB

  17. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435162483641:dw|

  18. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    do u know it?

  19. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    You are getting it slowly.

  20. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    just need the basic concept here like how do u find the resistive inertial force for a simpler question

  21. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435162643921:dw|

  22. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    mr + FBCosH = Fg , FBSinH = r

  23. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    The moment at any point = 0

  24. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okk thats what i want, are u sure its just mr?

  25. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    u have to add frictional force too there dont u

  26. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    m = friction coefficient , r = reaction. Just those

  27. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    maximum friction force = mr . So as to ease things I add mr directly.

  28. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    reaction force is sintehta Fb

  29. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    FBSinH = r

  30. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    we need this part too though|dw:1435162931881:dw|

  31. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435162940154:dw|

  32. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    im trying to remember, please clear the concept for me

  33. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Intertial force , Maybe up my grade level. Just ignore it.

  34. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    what does moment of interia give us exactly??

  35. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    isnt it a torque about that point

  36. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    maybe we can just completely ignored it?? there will be no rotation?

  37. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Bro, if there is inertial force. The problem 'd mention it.

  38. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    oh okayy alright then lets work now lol

  39. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435163176004:dw|

  40. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435163282223:dw|

  41. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    gotta write an expression for the horizontal distance from point C first as a function of the radius of the circle

  42. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    No need , just get the torque around (A).

  43. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    oh i know, umm since its root3 r, we can figure out this angle

  44. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1435163481985:dw|

  45. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Did you notice that AC is unknown too ?

  46. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yeah

  47. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    true, ugh just feels like root3 r is giving enough restrictions

  48. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Listen to me , Torque around (A) !

  49. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    okayy howw

  50. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Fb, mr will be omitted

  51. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    i dont really see how there can be any torque about A , should the tourque be about B

  52. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    R * r sqrt(3) = FG * r so FG = sqrt(3)R R = FG/sqrt(3)

  53. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Solved.

  54. dan815
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    nice, i still dont see how u did it

  55. TrojanPoem
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Get torque around (A), sum of forces up = 0 , sum of forces down = 0 , You get 4 equations with 4 unknowns solve and you will get tan ( I am using paper for ease :D)

  56. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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.