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imron07 Group Title

At what direction is the frictional force?

  • 2 years ago
  • 2 years ago

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  1. imron07 Group Title
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    • 2 years ago
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  2. BTaylor Group Title
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    The frictional force is parallel to the surface, opposing the motion. So, it would be pointing down the slope, if the drawing in the arrow represents the motion.

    • 2 years ago
  3. imron07 Group Title
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    Yes, the arrow represent the motion. But ummm, i'm not sure the frictional force is parallel to the surface, opposing the motion. Just like when we walk, the frictional force is in the same direction as our motion....

    • 2 years ago
  4. BTaylor Group Title
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    No, it's not. The friction always opposes motion.

    • 2 years ago
  5. RaphaelFilgueiras Group Title
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    |dw:1348327921150:dw|

    • 2 years ago
  6. RaphaelFilgueiras Group Title
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    |dw:1348328024524:dw|

    • 2 years ago
  7. BTaylor Group Title
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    the friction force reduces the acceleration of the object. When you are walking, the friction between your shoe/foot and the ground keeps your foot from sliding forward indefinitely.

    • 2 years ago
  8. RaphaelFilgueiras Group Title
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    |dw:1348328081329:dw|

    • 2 years ago
  9. imron07 Group Title
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    @BTaylor yes, it oppose the motion, but the motion of our shoes.

    • 2 years ago
  10. RaphaelFilgueiras Group Title
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    the a point is moving in rotation direction so frictions force oppose it

    • 2 years ago
  11. RaphaelFilgueiras Group Title
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    that's why the car can rise rump

    • 2 years ago
  12. RaphaelFilgueiras Group Title
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    get @imron07 ?

    • 2 years ago
  13. imron07 Group Title
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    @RaphaelFilgueiras : What about this:

    • 2 years ago
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  14. RaphaelFilgueiras Group Title
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    im talking about this

    • 2 years ago
  15. RaphaelFilgueiras Group Title
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    |dw:1348328369452:dw|

    • 2 years ago
  16. RaphaelFilgueiras Group Title
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    |dw:1348328561760:dw|

    • 2 years ago
  17. RaphaelFilgueiras Group Title
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    the friction is opposite to the moviment of weel

    • 2 years ago
  18. Mikael Group Title
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    |dw:1348328592225:dw|

    • 2 years ago
  19. imron07 Group Title
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    Yeah, i understand your explanation. But if we apply Newton's law, should we pick that direction too for friction to find system acceleration?

    • 2 years ago
  20. Mikael Group Title
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    the friction is opposite to the moviment of POINT OF CONTACT

    • 2 years ago
  21. RaphaelFilgueiras Group Title
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    yep

    • 2 years ago
  22. Mikael Group Title
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    Yes ma = mgsin alpha + f

    • 2 years ago
  23. RaphaelFilgueiras Group Title
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    f-mgsin(alpa)=ma

    • 2 years ago
  24. imron07 Group Title
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    Shouldn't \(mg\sin{\alpha}\) is in opposite direction with friction now?

    • 2 years ago
  25. RaphaelFilgueiras Group Title
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    yes it is opposite

    • 2 years ago
  26. imron07 Group Title
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    @RaphaelFilgueiras yes that's what I mean :)

    • 2 years ago
  27. Mikael Group Title
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    NO it is coincident with mg sin alpha : here is why (let me finish pls

    • 2 years ago
  28. Mikael Group Title
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    T|dw:1348328885247:dw|

    • 2 years ago
  29. Mikael Group Title
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    And when wheel is freely rolling the friction acts BACK on it

    • 2 years ago
  30. RaphaelFilgueiras Group Title
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    so your car never will rise the ramp!!!

    • 2 years ago
  31. Mikael Group Title
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    @RaphaelFilgueiras you are wrong : in his picture there are NO OTHER forces. The cart is only rolling up BY INERTIA and of course slows eventually. This is different from motorized climbing up !!!

    • 2 years ago
  32. RaphaelFilgueiras Group Title
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    the car is moving up

    • 2 years ago
  33. Mikael Group Title
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    The point of contact is moving a wee-bit slower than the surface - so the surface ACCELERATES it !

    • 2 years ago
  34. imron07 Group Title
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    @Mikael : So only when the engine turned on, friction will directed upward?

    • 2 years ago
  35. Mikael Group Title
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    YES @imron07

    • 2 years ago
  36. Mikael Group Title
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    And pls medal (-s)

    • 2 years ago
  37. Mikael Group Title
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    the vector is velocity. And please admit that I am right @RaphaelFilgueiras

    • 2 years ago
  38. Mikael Group Title
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    Again I clarify : When the wheel is free it serves as a friction-conduit from the surface to cart. When the motor is working the opposite: the wheel transfers torque from cart to surface

    • 2 years ago
  39. Mikael Group Title
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    It is a delicate but DRAMATIC CHANGE

    • 2 years ago
  40. imron07 Group Title
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    Well, i understand both of your opinion. But i agree with @Mikael . If the vector I draw is Force, would something change (engine on)?

    • 2 years ago
  41. Mikael Group Title
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    Of course - all is opposite

    • 2 years ago
  42. RaphaelFilgueiras Group Title
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    they are opposite but mg is greater than f

    • 2 years ago
  43. RaphaelFilgueiras Group Title
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    so it will stop,and then the friction and mg will be in same direction

    • 2 years ago
  44. Mikael Group Title
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    This time @RaphaelFilgueiras IS ok. Though he will never admit someone else IS .....

    • 2 years ago
  45. Mikael Group Title
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    The last remark of Raf is WRONG (again!)_

    • 2 years ago
  46. imron07 Group Title
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    You mean friction is downward even if the tire's working to move the car upward too?

    • 2 years ago
  47. Mikael Group Title
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    Friction is UPWARD when the tire PUSHES the surface (working) and downward when the SURFACE pushes the tire

    • 2 years ago
  48. Mikael Group Title
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    Both of you should imagine a tiny (really tiny) velocity difference betwee Contact point and surface. It has OPPOSITE directions in these opposite cases !

    • 2 years ago
  49. imron07 Group Title
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    @Mikael can you draw it please, (when engine turned on, and another force pull the car too).

    • 2 years ago
  50. Mikael Group Title
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    When wheel PUSHES it is faster downward - so frict is UPWARD

    • 2 years ago
  51. RaphaelFilgueiras Group Title
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    |dw:1348329423502:dw|

    • 2 years ago
  52. Mikael Group Title
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    |dw:1348329805336:dw|

    • 2 years ago
  53. imron07 Group Title
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    Okay, I understand now. Thanks @RaphaelFilgueiras & @Mikael !

    • 2 years ago
  54. RaphaelFilgueiras Group Title
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    yw

    • 2 years ago
  55. Mikael Group Title
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    You see the friction force is OPPOSITE to the RELATIVE VELOCITY\[V_{contact} - V_{\text{surface velocity relative \to wheel's center}}\]

    • 2 years ago
  56. imron07 Group Title
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    Yeah, that's what in my mind :D

    • 2 years ago
  57. Mikael Group Title
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    @imron07 and @RaphaelFilgueiras : Thank you both for educating me and all of us by your questions and thoughts.

    • 2 years ago
  58. imron07 Group Title
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    It was a nice discussion :)

    • 2 years ago
  59. Mikael Group Title
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    DUBITANDO AD VERITATEM PERVENIMUS !

    • 2 years ago
  60. Mikael Group Title
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    Veritas in disputando gignitur.

    • 2 years ago
  61. imron07 Group Title
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    What's that last phrase means?

    • 2 years ago
  62. Mikael Group Title
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    http://translate.google.com/#la/en/Veritas%20in%20disputando%20gignitur.

    • 2 years ago
  63. Mikael Group Title
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    http://translate.google.com/#la/en/PERVENIMUS%20DUBITANDO%20AD%20VERITATEM

    • 2 years ago
  64. RaphaelFilgueiras Group Title
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    |dw:1348331561351:dw|

    • 2 years ago