tug of war

Discussion in 'MCAT Study Question Q&A' started by unDRdog, 06.21.09.

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  1. unDRdog

    unDRdog 2+ Year Member

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    Chapter 2TBR passage 6 num 38 "According to Newton's Third Law, each team pulls with equal force on the other team. How, then, is it possible for one team or the other to win?"
    A-One team must exert a larger force on the other team.
    B-Winning or losing is determined by the net force on each team.
    C-blah blah
    D-blah blah

    Ok...how is it that A in in violation of Newtons third law outside of the question stem saying so? Would the "larger force" in answer a be refering to the force in the x direction only? therefore not being the net force. I'm confused...could someone break this down in a simple way....i freakin hate when i overcomplicate things...thank you...btw..correct answer is B
     
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  3. Dr Gerrard

    Dr Gerrard 2+ Year Member

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    I think there is a net force, due to friction.

    The forces on each team by the other team are equal and opposite, according to newton's law. However, one team exerts a greater force on the ground, and this is why the net force determines winning or losing.
     
  4. kobe200LATE

    kobe200LATE 2+ Year Member

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    I think the key concept that this question is trying to test you on is the concept that Newton's 3rd Law only applies to two objects exerting forces on one another. In this case, choice A would be wrong because by pulling the rope, the teams don't exert forces on each other, but they exert forces on the rope.
     
  5. sv3

    sv3 2+ Year Member

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    I think the question itself kind of led you astray: "....team pulls with equal force on the other team." For the question to state that, I can see why the OP thought the Forces equal.

    In any case, I was wondering if someone could confirm something for me. If you are drawing the vectors, friction would actually be in the same direction that each team pulls right? So fricton helps prevent the team from going towards the other team?
    Just something i was thinking about.
     
  6. Doodl3s

    Doodl3s 5+ Year Member

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    When I first saw that Question I saw two things wrong with answer A... first, F=ma, so a larger force doesnt guarantee a win since if the other team is a lot less massive they'll accelerate into the middle (losing)... ALSO, yea, neither team can exert a larger force anyway since all their force from both side is put into the rope, which then becomes equal and opposite, so theres really the same force on both teams. I don't really like B either, but thats how I'd eliminate A.
     
  7. loveoforganic

    loveoforganic -Account Deactivated- 2+ Year Member

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    Sounds right to me. To illustrate it better, imagine one team playing on ice, the other on cement. The team on ice doesn't have nearly the same frictional force helping them, and they're doomed to lose.
     
  8. sv3

    sv3 2+ Year Member

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    to expand, would you say the heavier team wins in this case?
    I think they have two things going for them.
    1) the other team will accelerate more since they are lighter
    2) the force of friction helps the heavier team as its built off the normal force
     
  9. Doodl3s

    Doodl3s 5+ Year Member

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    yea... more or less @sv3... however, i WOULD like to see choices C and D to see if they would have tempted me... cause like i said... B is not really worded that great either
     
  10. sv3

    sv3 2+ Year Member

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    Niiiice. Way easier than me going back and fourth in me head. I can see why you like the intuitive thing. I gotto make a better effort to think like that. Usually, I just attack problems and generally only think when the problem is tougher but examples like these make me want to think all the time......go figure
     
  11. loveoforganic

    loveoforganic -Account Deactivated- 2+ Year Member

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    The other thing to consider would be how the team positions itself. The larger percentage of the force the team can direct into the ground, the larger frictional force the team generates.

    And yes, stuff is a whole lot easier to remember if you have intuitive ways of thinking about it :p
     

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